Q&A Is reinstalling Windows needed after changing AV?

Captain Holly

Level 1
Verified
Jan 23, 2021
45
I have a very noob type question, I searched here and Google but did not really find my answer. I am on Windows 10 2004 with 8 GB ram on a basic laptop. I have used several AV programs over the last 6 months, including WD, Bitdefender Free and the paid Bitdefender Antivirus Plus. I also tried out KSC Free a couple of times in the last 3 or 4 months. I tried out the different AV's looking for one I liked well enough to keep. I downloaded Avast Free a few days ago and so far it is working fine. Before I downloaded Avast I did a system restore back to the previous version of my laptop with WD. Then I installed Avast and I believe I will keep it.

I am wondering if it is necessary to reinstall Windows again since I have changed AV's so many times recently, or is my system restore back to a known good point all that is really needed? My laptop runs fine now and I have no trouble with the internet speed or running programs. I don't have a system image but I do keep copies of important files like pictures, music, and documents on flash drives so if I did need to reset or re-install Windows that would not be a problem. The Avast Cleanup scan said I have some 200 or so broken registry files, which is what prompted me to think about resetting Windows.

Thanks for any input on this.

Cpt. Holly
 

brambedkar59

Level 22
Verified
Apr 16, 2017
1,175

Is reinstalling Windows needed after changing AV?

Short answer: No
Long answer: Not necessary unless you are having issues. Even then I would try other things first before going nuke. If you are really into trying AVs out I would make a system image first just for peace of mind.

The Avast Cleanup scan said I have some 200 or so broken registry files, which is what prompted me to think about resetting Windows.
Registry cleanup tools are mostly snake oil. I would stay away from them as far as possible.
 

mlnevese

Level 24
Verified
May 3, 2015
1,375
As @rockstarrocks said, not at all unless you have problems. Windows 10 is actually good at self-repairing most of the times. I have a 4 years old computer that had at least 3 different products installed and uninstalled, not even counting second opinion scanners and is rock solid. Never had to reinstall.

Also keep away from registry cleaners. They mostly cause problems with 0 gain.
 

SecureKongo

Level 21
Verified
Feb 25, 2017
1,086
Depends on the AV from my experience. After installing Sophos Home on a non-clean windows system, I faced some problems like some modules turning off by theirselves for no reason after reboot etc. I then decided to do a clean install of Windows as I didn't do it for quite a while. The first thing I did was installing Sophos Home again and since then not a single problem and barely any system impact.
 

Gandalf_The_Grey

Level 50
Verified
Trusted
Content Creator
Apr 24, 2016
3,919
Another great tool is Antivirus Removal Tool:
Antivirus Removal Tool is divided in 4 sections:
1 – Identify the currently installed antivirus programs.
2 – Search for leftovers of past installations of antivirus programs.
3 – Uninstall using Windows built-in functionality.
4 – Run the specialized uninstaller provided by the manufacturer.
Especially option 2 is particularly useful.
 

roger_m

Level 34
Verified
Content Creator
Dec 4, 2014
2,320
It's not needed. However, I highly recommend running the vendor's own uninstall tool after uninstalling an antivirus. Quite often there will be some drivers which don't get removed when you uninstall an antivirus. These leftover drivers, are sometimes still loaded when you boot Windows and cause issues with other antivirus you install. Running the vendor's uninstall tool will usually remove these.
 

blackice

Level 33
Verified
Apr 1, 2019
2,198
It's not needed. However, I highly recommend running the vendor's own uninstall tool after uninstalling an antivirus. Quite often there will be some drivers which don't get removed when you uninstall an antivirus. These leftover drivers, are sometimes still loaded when you boot Windows and cause issues with other antivirus you install. Running the vendor's uninstall tool will usually remove these.
I’ve never had trouble with leftover drivers after using an uninstall tool from the vendor, this is great advice.
 

Chuck57

Level 6
Verified
Oct 22, 2018
262
Start with Macrium Reflect and a clean OS, and all your programs freshly installed and ready. Do a backup to an external drive. Then have fun trying various antiviruses or whatever else you want. When things start getting bad, restore the image. I've been doing it for quite awhile, through 4 restores. You're only talking 12 or 15 minutes with Macrium to make the image one time, and another 15 minutes or less to put things back the way they were. If you have SDD drive probably less than 5 minutes to image and another 5 or less to restore.
 

blackice

Level 33
Verified
Apr 1, 2019
2,198
Start with Macrium Reflect and a clean OS, and all your programs freshly installed and ready. Do a backup to an external drive. Then have fun trying various antiviruses or whatever else you want. When things start getting bad, restore the image. I've been doing it for quite awhile, through 4 restores. You're only talking 12 or 15 minutes with Macrium to make the image one time, and another 15 minutes or less to put things back the way they were. If you have SDD drive probably less than 5 minutes to image and another 5 or less to restore.
There are some drawbacks to this. Sometimes when reimaged M$ store items not on the C: won’t be recognized. You have to uninstall them BEFORE reimagine because if you don’t you’ll have to format the drive they are on to reclaim the space. You cannot manually delete them.
 

Captain Holly

Level 1
Verified
Jan 23, 2021
45
Thanks for all the advice here. I used the Bitdefender Free and Paid removal tools to remove both versions of Bitdefender. It took some searching though to find the remover for BD Free, I found it here, thanks to the MT forums. I ran the Kaspersky removal tool and there was a Kaspersky folder it left over that had about 8 different files in it, I could no get rid of it and it was preventing WD from turning back on. Revo could not get rid of that folder either. So I did a system restore and that took care of it. I went back to WD for a week and made a system restore point with WD and that is the one I restored to before trying Avast. I will run the BD and Kaspersky removers again just for good measure. Thanks very much for the help on this.

Capt. Holly
 

Captain Holly

Level 1
Verified
Jan 23, 2021
45
Another great tool is Antivirus Removal Tool:

Especially option 2 is particularly useful.
Thanks Gandalf, I ran this for Kaspersky and it must have found a few leftovers because it took several minutes to finish. I ran it for Bitdefender too and those must have uninstalled clean the first time I ran their tools because the AV Removal Tool did not run at all, right away it said BD had already been removed.

Thanks.

C.H.
 

Chuck57

Level 6
Verified
Oct 22, 2018
262
There are some drawbacks to this. Sometimes when reimaged M$ store items not on the C: won’t be recognized. You have to uninstall them BEFORE reimagine because if you don’t you’ll have to format the drive they are on to reclaim the space. You cannot manually delete them.
I haven't had a problem, that I've discovered anyway. I did a full image, all partitions, and I think all are formatted before restore, and the restore puts it all back.

I keep all my documents and other files on an external drive and work from the external. No files or downloads stay on the hard drive. I thought maybe I was finally doing something right for a change.
 

Captain Holly

Level 1
Verified
Jan 23, 2021
45
Short answer: No
Long answer: Not necessary unless you are having issues. Even then I would try other things first before going nuke. If you are really into trying AVs out I would make a system image first just for peace of mind.


Registry cleanup tools are mostly snake oil. I would stay away from them as far as possible.
Yes I agree 100%, and am not using the Avast Cleanup utility, I don't think it is really needed nor does it do anything Windows itself can not do, but Avast did run its cleanup scan when I first installed Avast.

C.H.
 

plat1098

Level 25
Verified
Sep 13, 2018
1,419
@roger_m : sorry, too lazy myself to check this right now, but have you found HiBit to be comparable in successfully removing name-brand antivirus remnants? Like all of them: drivers, registry keys, folders.

I figure: if you already have something like HiBit (or other good uninstaller), you would not need to d/l yet something again. I think drivers for many software have been improved. It used to be that a corrupted driver would increase the chances of having to reinstall Windows. But currently, not having this issue for the past several years.
 

fabiobr

Level 12
Verified
Mar 28, 2019
551
Depends on the AV from my experience. After installing Sophos Home on a non-clean windows system, I faced some problems like some modules turning off by theirselves for no reason after reboot etc. I then decided to do a clean install of Windows as I didn't do it for quite a while. The first thing I did was installing Sophos Home again and since then not a single problem and barely any system impact.
Avast sometimes has the same issues here. I had to download AV removal/uninstaller to remove files that stayed from the previous AV.

Another great tool is Antivirus Removal Tool:

Especially option 2 is particularly useful.
Does Revo Uninstaller do the same work?
 

geminis3

Level 18
Verified
Sep 10, 2015
859
TLDR: It depends of the AV

On my personal experience ESET has the cleanest built-in uninstaller followed by Avast (which requires an special tool), Kaspersky it's not good but Bitdefender is the worst and can easily damage your Windows install and leave tons of letfovers even after using their special tool.
 

fabiobr

Level 12
Verified
Mar 28, 2019
551
There are some drawbacks to this. Sometimes when reimaged M$ store items not on the C: won’t be recognized. You have to uninstall them BEFORE reimagine because if you don’t you’ll have to format the drive they are on to reclaim the space. You cannot manually delete them.
Yeah, one time I didn't know that and I had to format the drive with all my games because of ONE Microsoft Store Game (Metro Exodus).

I learned the lesson and now I install MS Store games on a separate drive.

TLDR: It depends of the AV

On my personal experience ESET has the cleanest built-in uninstaller followed by Avast (which requires an special tool), Kaspersky it's not good but Bitdefender is the worst and can easily damage your Windows install and leave tons of letfovers even after using their special tool.
Same experience here.
 

Dex4Sure

Level 3
May 14, 2019
111
Short answer: No
Long answer: Not necessary unless you are having issues. Even then I would try other things first before going nuke. If you are really into trying AVs out I would make a system image first just for peace of mind.


Registry cleanup tools are mostly snake oil. I would stay away from them as far as possible.
I just remove the traces manually from registry myself... Not hard to remove most of the traces manually. But yeah system image back up is recommended. Registry cleaners can do damage in the registry by deleting keys that were in fact in use, so I would never use them.
 

blackice

Level 33
Verified
Apr 1, 2019
2,198
TLDR: It depends of the AV

On my personal experience ESET has the cleanest built-in uninstaller followed by Avast (which requires an special tool), Kaspersky it's not good but Bitdefender is the worst and can easily damage your Windows install and leave tons of letfovers even after using their special tool.
I’ve found Bitdefender uninstalls very cleanly these days. At least last summer when I tested it last.
 
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