mine is an OLD HCL desktop. i haven't started my pc for about a month. now when i started my pc my HDD is detected by mine motherboard and then the screen comes to CHOOSE how to start the windows(normal,safe mode etc.)i choose any mode than windows start up screen comes and than it reboots.if you want any other information please REPLY
Tap the F8 key as the computer is starting. This will open the advanced startup options. At that screen choose Disable Automatic RESTART on System Failure.

See if that will stop it from rebooting and give you an error message. If you can get an error message, post it in your next reply. Post the entire error message.the error message was 
STOP:0x00000024 (0x00190203,0x86570828,0xc0000102,0x00000000)See if can boot through safe mode with command,then go to ur start menu,click on run and type this 'chkdsk /f and press enter,click y for yes and restart the system.i tried opening with safe mode. as soon as i opened a black screen come checking my different drivers and then it reboots Quote from: shaurya21 on November 02, 2011, 11:58:31 PM

the error message was 
STOP:0x00000024 (0x00190203,0x86570828,0xc0000102,0x00000000)