Computer won't boot, not even in Safe Mode or anything, also tried reinstalling Windows with CD but won't boot?

I was on my computer (Windows XP Media Center Edition SP2) for an hour, after I was done using is I turned it off.

Note: I know its not a hardware problem, because I uninstalled some game before turning it off. I was uninstalling the game, and accidently turned it off when it was uninstalling.

I tried turning it on but the Windows loading screen was there for an hour! Tried again 3 timea, then tried to go into safe mode and any other stuff.

I even tried reinstalling Windows. When I tried to boot from the Windows XP CD, the screen just went black. When I tried Windows Vista, I was staring at Windows Vista loading bar for an hour. What do I do?

And please guys, don't tell me to remove the hard drive or anything or telling me to get a slave drive...I'm only 13 years old .