XP hangs on Loading Screen

Hello,

I have an unusual problem with my PC, every time i turn off/stand by/hibernate my machine and don't turn off the mains(Power Supply) to the CPU, my PC will get struck on the Windows XP Loading Screen(Just Before the User Login Screen) the next time i boot/power on! But once i turn off the switch and turn on and then start my machine, everything goes smooth and windows loads as usual.!!