When I've run into this kind of problem, it often involves the files on the 
hard drive necessary for the computer to boot up having become corrupted.

Since the computer lacks a floppy drive, you would need a bootable CD to see 
whether you can in fact still boot the computer, as well as try to repair 
the problem.  Either the original Windows XP DVD or something like the 
"Ultimate Boot CD" can give you a chance to see if the system will boot (you 
may need to change the boot order of your drives in the BIOS or Setup, 
placing the optical drive ahead of the hard drive).

Before doing this, I'll usually pull the suspect drive from the computer 
that it is in and place it in another to see whether I can still read the 
files.  I'll back up all the important data files at this point, and I'll 
take the opportunity to run a thorough virus and spyware scan on the disk. 
Finally, I'll run the windows error checking feature on the drive and hope 
for the best.  (A bootable CD with a mini-operating system, like Bart's PE, 
may be an alternative for these steps, if you don't have access to another 
computer.  However, you'll still need access to another computer in order to 
download and burn this CD.)

As someone else has suggested, it may be that the drive is physically dying. 
If error-checking doesn't get the drive to boot the original computer or you 
just want to be more thorough, I would find the hard drive manufacturer's 
diagnostic utility and do a thorough scan of the hard drive.  These can be 
found at the manufacturers' websites, and the "Ultimate Boot CD" comes most 
of these tools included.  If the drive passes the diagnostics, I would write 
zeroes to the whole drive and start over.  Reformatting and re-installing.

I hope some of these ideas are helpful.

John Sproule 

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