Windows 7 blue screens/the system could not find the environment option that was entered (ask for any more details, Yahoo word limit)?

Well, the last 2 months or so, I'd be on Skype with friends playing games like MW2, or Battlefield 3, but each and every time, after about 5-15 minutes into the game (also happens when I play games on my own now) my screen would freeze for 1-2 secs, the speakers would buzz, and the system would go blue screen.The follow up was that the PC would have a bit of a hard time restarting, and when it would, and I'd try to reopen the game, it'd crash again.After a few times, this had gone to the point where I could no longer easily turn on my computer.Each time it would go until the Windows loading screen, then it would either bue screen me again, or it would self-restart.Startup repair would function, but I was neither able to restore my system (claimed I had to dates stored, although I remember doing this before and having a ton in front of me), nor would it find any flaws.Except one time, it did, and I was finaly able to get past the Windows screen. I opened up a game and the same happened again, except I was able to recover faster this time. Now my machine is somewhat slower on startup, and I seem to lack admin rights, for I cannot open downloaded files, or use certain functions of the computer (e.g accessing Advanced System Settings on the control panel).Each time I try to do any such thing, I get an error message saying "the system could not find the environment option that was entered.I've looked into solutions, but so far no luck, and I can't bother formatting again.Any idea?