Hideous Virus from Hell!!!

[sbutler]

I've been applying for new jobs lately and I keep getting thousands upon thousands of junk emails offering scam jobs etc and I think one of these has infected my laptop, I tried to system restore but it kept coming up with an error message saying "System restore was turned off by group policy to turn system restore on please contact domain administrator" so then I tried the registry thing and again it said it had been turned off, and then I tried running it in safe mode but when I restarted it, it then would not bring my profile up and just keeps saying "Other User" and asking for a user name and password, and of course there is no other user, I have tried running it in every single mode and nothing is working, I already have my hard drive backed up externally, so I'd be happy to wipe it clean and start again, as the laptop was a present from my Dad just before he passed away and I don't want to lose it. How do I fix this? How do I wipe it clean and start again? Please help!