Stuck on "starting windows" after it was working FINE!

Hey this is probably my first time ever creating a thread on troubleshooting something about my PC.okay lets startoff that in the very beginning i had XP and decided to upgrade to Windows 7 ultimate x64. It worked out awesome no problems. Last night i was playing a game and i fell asleep on my bed. i woke up in the middle of the night and shut it down with the power button method. This morning i wokeup and i couldnt get into windows, it just wouldnt boot up. I tried doing the repair, restore, nothing worked. I was just stuck on "Starting windows" screen, it was really random. I tried reformatting with windows 7 thinking it would fix the "starting windows" problem but it just kept getting stuck after the fresh install of windows 7. I've wasted 7 hours of my day just frustrated/pissed trying to see wat can possibly be causing this problem. The thing is i went back to installing XP and it works fine. Which is wat im operating under now. I even tried installing XP and then reformatting with windows 7, and nothing..same exact problem getting stuck on the loading screen after the format was done. Could it be BIOS? I cant think of anything else. Especially when windows XP is working, its not like one of my hardware devices are defected. Its just weird because just last night windows 7 was working fine. I dont know wat couldve went wrong just from the time i shut it down to the next morning when i wokeup and i couldnt get past my loading screen. And about my computer knowledge ide say im not total newbie..but im pretty mediocre at common sense troubleshooting problems i usually encounter..i just dont see wat else to do after a fresh clean install of an OS usually that solves most problems. I have a EVGA 790i mb, 2gb ocz sli ram, 1tb Western D HD, 9800gx2. All the help is appreciated, Thank you.