For Windows 7 :
What made you change from Avast apart from trying MSE?
Other Free AV software :
On-Demand scanners :
Browsers Plugins :
This are a few plugins that will make your live more easy and comfortable:
Visualization:
Even if you submitted a file to virustotal.com and it said that it's clean , you'll need to run it in virtual environment because sometimes infection can be so new that security vendors don't have signs for it.
Visualization software will allow you to browse the web or run another application in a completely safe environment. This is especially useful when visiting high-risk web sites, whether accidentally or deliberately, as the Web browser will be completely contained within the virtual enviroment, preventing any damage to your computer.
A sandbox can also be used to run any other applications which you think may be suspect - you can run the program inside the sandbox to determine whether or not it is safe while remaining completely protected against any malicious actions that it may try to carry out.
I strongly advise you to install Sandboxie and use it when you're browsing the Internet or running shady/unknown programs.
Alternately you can try
BufferZone PRO (Free) , another great virtualization software.
Sandboxie (Free/Paid) -
link
Sandboxie runs your programs in an isolated space which prevents them from making permanent changes to other programs and data in your computer.
Always run suspicious of freshly downloaded files in a Sandboxie to verify that he download isn't compromised!Sandboxie will replicate perfectly your operating system so all the files should run without any problems in it.