System Restore is one of the first features of Windows that many viruses try to disable. Do a full system scan with your antivirus program, but this may not be to productive if a virus has already snuck around your antivirus program. It is a starting point though.
Also, like Matan requested above... give us some more info....does system restore run but fail at the end of the process, or does it just not run at all?
Aford10 is correct about Safe Mode and you should try a Safe Mode Restore of your System Registry first. That would be the smart path in the troubleshooting path.
If Anonymous is infected with one of the new variants of the identity theft viruses/hostageware coming out of Russia right now (and we are seeing lots of them), then he/she will likely find that safe mode hangs during startup. We have not been able to access Safe Mode on many of these new infections until the infection is crippled.
If you can not get into Safe Mode, I use a utility boot disc called MiniPE with a Registry Restore program to resolve these types of infection. If, as Aford10 says, the restore points haven't been deleted MiniPE will allow you to restore an earlier restore point. The virus infection will still be on your computer and you will have to scan for it, but now you shouldn't be prevented from doing so.
Again, more info on the symptoms you are experiencing would be nice.