My younger brother is absolutely clueless about computers, he's 13. I visited him earlier today and he committed the irreparable: he installed Frostwire and downloaded stuff off it. You know what that means. Anyway, I noticed he gets a BSOD at the OS login screen. I know that I can simply login into safe mode, run a Malwarebyte's, Avast!, all good...but yea some stuff just won't go and I don't have that amount of computer knowledge. Also, re-installing OS is not an option as the CD is lost and well, it's not exactly a high-end computer so I don't think I'd be willing to buy another. I definitely don't want to pirate a copy either, since it's just wrong.
Anyway I just want to know how to put his computer back how it was say, a week ago. The damage have been caused roughly 2 days ago, and nothing important is on the computer. Any tips on how to do it? I've seen it before, and I remember doing it for myself a long time ago, I just need refreshers.