Windows 7 - System restore fails after Avast Antivirus messes up the system

I ran a full scan on Avast yesterday, it found 3 infections in my windows folder, can't remember the specific paths anymore.. I think one was in Sys64 or something.
It managed to quarantine 2 of them but it couldn't find the specified file path (or something) of the infection in Sys64 (or something).
So, Avast suggests that I restart and run a scan. I click yes, computer restarts, starts running a scan before Windows starts. After an hour it is done, I log on my account...

The startup is a bit faster than usually, but I notice that the programs that should start on startup won't (MSN Messenger, Skype, etc. including Avast itself. Comodo firewall starts as it should though).

I try to open some programs, including Firefox, Avast, Messenger... nothing happens when I click the shortcuts.
I can use explorer to browse my folders, but if I try to open an application nothing happens (usually, CCleaner worked however).

I tried system restore to an earlier state, but once the restore was "done" and I logged back in, it said that system restore failed because an antivirus program was running a virus scan.

I tried to clean registry and remove some files with CCleaner, but no effect.
I also tried to system restore to a different point multiple times: same effect. Fail.

So I tried to uninstall Avast, nothing happens when I click it at the control panel "uninstall or change programs" thing.

Next I go on rampage and try to delete the folder of Avast Antivirus, it says I need admin rights for that.. I have.

... what should I do?

Seems Avast definitions are flagging important system files as infected. Many are saying sfc/scannow corrects the problem.

Just check the Avast forum and you'll see how many current threads there are on it.

Might be time for a new AV App. MSE is a very good alternative.

Thanks a lot, Airbot! It worked!
Also, Ted: indeed. It's gonna be either AVG or MSE.