Reboot HP PC

After I try booting in safe mode, last….and all the basic procedures my pc is not able to reboot. I already put the hp home edition win xp to reboot and it did not work, I also try the office xp and nothing. It shows like if is going to reboot but it goes back to the blank screen to choose safe mode etc…I have try pressing F10, F2, F8 and I got this blue screen saying A problem has been detected blah….UNMOUNTABLE_BOOT_VOLUME
if this is the 1st time that happens restart your computer……I know the very basics on computers and have done reboot to other computers before but this one just seems to give me a problem please help me out to find out what it is or at least have an idea why this happens. The monitor is a flat screen and is also use as a TV.

Thanking you in advance