blackscreen after crash, after reboot...

hello

today 19.50 hi was sitting after my screen for plus 4 hours, i was playing battlefield 2142 for 10 minutes and the game seemed to be stuck. fot that game not so strange, it happens more, but this time the sound kept on playing the same gunshot, and i couldn't do enything. the whole system was stuck.
even the stand by function of the case powerbutton didn't work. so i resetted my config. after the xp professional loading screen i see my cursor. but that's all! i can't move it, and the background color is black! (black is no color i know).

so i again rebooted, xp started up, but after 5 minutes the pc got stuck again! I rebooted for the 3rd time, and yes, now i am typing at my system.

i remember that at 14.30h i closed down my pc, and i had 7 xp updates! so i just let windows install them, because i can't do something while i'm in closing screen.

my sister at the other hand, had the same thing with a vista computer today. i put a new wifi pci- card in both computers, but i don't think that could be the problem because i used 1 of the 2 in my own, and never had problems.

so, do you guys heard of weird problems with the latest windows updates that give black screens? or make the pc get stuck?

i don't know what it is, but my sister's notebook had it also now. (3 computers in the same building!)

help please, thanks