Window XP and Vista keep poping off on Windows and linux dulboot
 

Both Xp and vista will just pop off not saying anything and just reboots. I installed Mandriva 2008 it works perfict I even formated C drive and reinstalled Windows but it still hapens.could I be having powerserges linux runs grate PS I love Mandriva it finds all my hardware for me.by the way how can I install Windows under linux that is boot linux and run windows that way thanks to all you smart linux users.

What do you mean 'pops off'? Does it boot, you log in, and it reboots? If it does, that sort of behavior (especially if its somewhat erratic) usually indicates a defective or too small a power supply and you'll need to check the power supply specs against the power consumption figures for all the stuff you've plugged in (video card, HD, CD drive, MoBo ...)

I don't mean to be a asshat, but what exactly is your question? Would you please use punctuation? If you are asking why you can't see the bootloader after formatting C and installing windows, it's because windows rewrites the MBR (main Boot Record). If that is not the question, please help us help you by using a more clear and concise language.
Thnx

VMWare or virtualbox.

ok,the problem im having,its not the boot loader. I know about all of that. AT any given moment that im running windows, if i try to open any program, say IE,the power will shut off, and the computer reboots not showing any error or anything. I do have my fans hooked up to my power supply but to a cable that does not go to a drive, thats because, I dont think my fans run at all when hooked to the mother board. Im going to hook them back to the mother board and just run windows and see what happens. ACPI is working because i can tell what my temperature is, but i dont think my fans are ever running, what temperature do u think the fans should kick on?

I have seen that thing happen before to cracked versions of windows. Or it could be a virus. Also, you might want to check under the fan of your cpu, see if it's caked with dust. Whenever the cpu reaches a certain temperature the motherboards will turn off the compy and it ussualy overheats if there's a lot of dust blocking the airflow through the coolers.
The fans should be running regardless of the temperature - try just connecting them to the 12v plugs coming out of the PSU or try a different fan.