@Mallorie Hey! If you want a free alternative, i would personally go with Avast! (just don't install their browser add-on) paired with Windows Firewall and you are good to go.
If you want paid and light antivirus solution, you can go with ESET Antivirus or Emsisoft Anti Malware as
@exterminator20 @illumination @jamescv7 @Kent suggested you can try a trial version of both see what suits your system better. If you have a good CPU and a good amount of RAM you can use Kaspersky Antivirus(
@Tony Cole suggested the KIS suite which is quite good but it's a bit on the heavy side).
You can pair one of the above with either Malwarebytes or Hitman Pro, accompany that with a backup solution like Acronis True Image or you can just make a system backup to an external hard drive through Windows "Backup and Restore" .
For miscellaneous tune up utilities, what the guys have posted above is spot on.
P.S. You can also try Webroot, it's know for it's lightness though it works differently as compared to traditional AV so it might not be down your alley. Give it a shot though if you want to try something different.
Cheers