So if you want to nuke your os, loose all your data, configuration, setup, game saves, utils etc, nuke your os. Easiest and most reliable way to go is reloading os.
As for restore to an earlier point, doesn't work, I've seen this a lot, and it never worked.
Couple months ago I found the fix for it.
Step 1: Find some way to remotely edit the file system, you'll need to be able to both copy folders and edit the registry. I'll let you decide what utility to use for that, but googleing UBCD is a good place to start for sure. There's a couple offline registry editors in there, but I mostly use the one disguised as a password removal tool.
Step 2: navigate to \*****\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
make sure there is a key there named Userinit and it's value is C:\WINDOWS\System32\userinit.exe, (<--note; Comma is not a typo... I don't make typo's
******<---depending on what utility you're using to edit the registry, this can change, so just gotta look through them.
Step3: Once you have that, the rest is a cakewalk. Boot off your windows recovery cd's, and go into the repair mode. This will give you a cmd prompt. Find a clean userinit file (either off the recovery cd which you will have to unpack, or out of your C:\I386 folder) and copy it to C:\Windows\System32\userinit.exe
For me this has worked every time. If you can't figure any steps out, let me know and I can expand upon them with a lot more detail. Other than that, any local repair shop should be able to handle it.
BTW... if this works, when you do get in to windows, save EVERYTHING. If your infected, the problem will return as soon as you reboot.