System Restore

[Cg.]

I probably downloaded something infected with a virus or
something that corrupted some system data (A couple
programs wouldn't work right and outlook was sending some
odd emails) So I went to use system restore, but when I
clicked on it a message popped up saying "system restore
is not able to protect your computer. Please restart your
computer, and then run system restore again. But after I
restart or shutdown it comes up with the same message.

Any help would be greatly appreciated.