My computer shuts down by itself every 15mins or so. Then the black screen with these message:
"Windows could not start because the following file is corrupt is missing or corrupt
\WINDOWS|System32\CONFIG\System."

Sometimes it reads: "The keyboard is missing or not connected... Floppy disk drive error"... something like that.

Please help... before my computer shuts down again. Thanks

Suggest you take computer to a reputable local service center for diagnosis. I'd wager a power supply or drive problem, perhaps overheating. Next normal boot, if you are running Windows, stop the boot process at Windows startup menu by pressing F8 immediately after POST and let the computer sit for awhile. See if it still eventually reboots. If so, hardware issue.

Hi

First you check any hardware IRQ that reasons may be 1. fault memory 2. power supply unit voltage rating not matching (such as 220v PSU attached to a240v mains outlet)
Intermittent power to hard drive or other parts
Faulty hardware
The troubleshooting is start-run-sysdm.cpl-advance tab-startup and recovery-settings-(unclick automatically restart)ok-ok-restart your computer
That only easy to stop automatic restart or shutdown