Is this computer part of any network? If so, check with your admin person. If not, to turn on/off system restore, go to the System Properties window (while holding down the button with the Windows logo in the lower left portion of your keyboard, hit the Pause/Break key in the upper right). There is a tab at the top for System Restore. Click on that and you'll be able to turn on/off system restore. Have you run virus/spyware scans? You need to make sure you're clean first. If system restore has been turned off, the best you'll be able to do is turn it on, as you won't have any restore points to restore to.
It is hard to fail, but it is worse never to have tried to succeed.