i have intel 2.8 dual core,256mb ram,geforce fx 5200 256mb,simmtronics moterboard. my computer shuts down after 5-10min & sometimes even 30-50min after i start a game,the computer wound not boot(manually) till 5-10 min after shut down.games work fine when i detach the graphics card.my graphics card works fine on other pcs.this problem started after an improper shut down when i had to replace matherboard's battery.

   The first place I would look would be the power supply (I am assuming it is a desktop computer).  Try buying a new one and replacing the old one with it.  That is the easiest way to tell if it is a bad power supply.  If not, you can use the power supply on almost all desktop computers so sooner or later you will need it.

Quote: games work fine when i detach the graphics card.my graphics card works fine on other pcs.this problem started after an improper shut down when i had to replace matherboard's battery

Looks like what has happened here is you have a conflict between the installed video card and the onboard video chip.
When you pulled the battery on the motherboard, you reset the CMOS chip. The BIOS redetected devices and found two video devices.
What you need to do is go back into the BIOS setup and disable the onboard chip if you want to use the video card. You did this when you originally installed the video card or you would have had this problem all along.