My laptop switches off iteself automatically

Hi, I have very strange problem with my laptop. My laptop model fujitsu amilo pro v2010 goes switches off itself automatically when booting form cd or run windows setup. I have two operation system installed separate on different partitions. Both are windows xp. If I select one os then it boots fine and starts the windwos but if i don't chose os then it switches off automatically after few seconds. When I choose one os then it works and start the windows but after windows about 40 minutes my laptop switches off itself again. I have checked my ram, Hdd with other one, It is fine. Even When I remove the hdd from laptop it also goes switches off itself. When I goes to bios then it does'nt switches off but when i exists from bios then again it switches off when i dont choose os from boot menu.

Please help me.

regards,
Neeraj