my computer shut down automatically while I was watching a movie.Restarting the computer, shows no sign on the screen but CPU fan is working as usual and loading of DVD drive and booting doesnot occur while PC LED is on. In other words just CPU fan works while rest is dead. The power led on the CDRom is also off. Yesterday, I was not able to shut down my computer using power buttom on the front panel, the switch on the back of power supply was the only option. While I can log off or go to sleep mode but shut down function did not work. I also checked all the connections and cleared BIOS but no use. Another important observation is that immeditely after its automatic shutting down, I restarted and on the screen it was stated that CPU speed was changed and I was asked to press esc or F1 to continue, i pressed F1 and therafter, i could do nothing, no matter even i cleared BIOS. I cannot figure out the reason. any suggestions?