If you had something on your system before, it is likely that System Restore made a backup of your infected files and that is what your antivirus is detecting.
The proper way to rid your PC of an infection, should you have one, is to turn off System Restore before removing it, that way it won't make a backup of the infected files...and it also will clean out the restore folder.
Most antiviruses can't clean the Restore folder because Windows locks it and won't let them.
The remedy for you right now to clean it up, is
- turn off System Restore
- turn it back on
- reboot again
- set a new restore point (right away!)
Until you do this, I would not trust any of your previous restore points as being clean and trustworthy.