window protection error

hi, i'm Pat_001.
I just registered today, so sorry if i'm a bit confusing. My friend and I were working on his computer at my place today. After the splash screen comes on, Windows (he has Windows Me) starts loading, but right after the desktop finishes loading (It asks to restore my active desktop), the screen goes blue and in the center it is written, "Windows Protection Error. You need to restart your computer. System Halted." It's kind of wierd because i did almost everything (including taking the entire computer apart, seriously) and i still couldn't get that message to go away. Do you have any ideas on how i can get that to dissapear and run Windows again? And what should i do to it? Should i keep Windows Me, or put XP on instead? I prefer XP (but it doesn't dtop the message). Or should i just fix the problem then change it?