Well, at least we have something going. I recommend you backup your files to your other comp or just anywhere like a external hard drive/ flash drive.
I also recommend you turn on System Restore so we can at least rollback to a better point of stability (aka now)
Start Menu---> computer ---> properties----> system protection ---> select your hard drive---> configure
Select "restore system settings and previous versions of files" and use the slider to reserve a good amount of space. A few GB is good enough, you don't need like 12% like the thing may ask.
Then go to start menu and type
system restore and choose "create a restore point"
As for Avast, not sure what to do with it for now, but an alternative is
Malware Bytes It's the one I use. The free version doesn't have on demand protection though but manually scanning once in a while helps a lot. They also have a free trial for the real time protection that can hold you over for a little bit.