My computer keeps reseting when the logo show

Hello,

i've just tried to turn on my computer desktop its a windows xp and worked fine everyday
however just now there was a power out and when i turned it on this time it came up with a black screen with 5 choices:

Safe Mode
Safe mode with networking
Safe mode with command prompt
last known good configuration
start windows normally

i know what these all mean but once i tried one - it reset the computer as the windows xp screen was loading with the blue bar
so it hought i'd try the rest and yes, it didnt work one bit .
i tryed using safe mode F8 but it still keeps reseting when the logo of xp shows it loads greet but then whene its loading the threed bar some where in the middle it stops loading and it reset the computer and thad every time

so i need some help in actually getting on to the log on screen and not reseting the actual computer
Thanks