System restore points are stored in a hidden folder called System Volume Information on the root of the C: drive.
Before you can find it, you will have to go to Folder Option > View > Uncheck "Hide protected operating system files " and check " Show hidden files, folders and drives ".
After you have found it, you will have to "Take ownership" to open it, and some steps I don't completely understand.
So, that's all I can tell you.
Google for the real and complete answer. There must be a complete tutorial compiled by Shawn aka Brink.