Unique Windows problem

Hi, I think I have a very unique problem in that I haven't been able to find anything similar about it anywhere and I've been searching for days. I'll decribe it in-depth. So a few days ago I was playing a computer game that requires maybe medium to high processing and video power to play (Europa Universalis 3, if any of you have heard about it) anyway, so I was playing this game and then had to turn my computer off using the power button instead of the usual shutdown because I was in a hurry. When I get back and turn on my computer, it works fine and I am able to sign in and start to go about my business, however, about a minute after I turn my computer on, it freezes. I can still see what I was doing and my mouse and everything, I just can't move my mouse and the screen is frozen. I then proceeded to look up fixes on the internet on another computer, turning up nothing about my particular problem. It starts up in safe mode only but not in normal mode. I have tried everything, a system restore, a registry clean, defragging my hard drive, but nothing works. I have heard that it may be a hardware error, especially since I have an nVidia video card, and I have also heard that it is definately a software and not a hardware problem. At this point I have no idea whatsoever on what to do and think I may have to buy a new computer, which won't be fiscally possible for quite some time. If anyone has ever heard of or expierienced this problem and knows how to fix it cheaply, it would be greatly appreciated. Thanks for reading my long description and for the help!