Well, there are probably a bunch of different ways, but if you can still click the start button and then on the "Control Panel" button on the start menu, try first to click on "Uninstall a program" just look down the list and try to find the program that looks like your malicious software (sort of like the old game of "which one of these things is not like the others"). Usually, they won't be able to be removed this way, but sometimes they can, and at least you can identify your culprit sometimes.

The system restore program is located in different places on different computers, but it should also be available under control panel > backup and restore center > repair windows using system restore.


Edit: uhh, or just do a Search for "System Restore"