A friend asked me to look at their PC because the vendor has never been able to fix it. Once every few boots, it says either "NTLDR manque" (french for NTLDR missing) or "error accessing disk" (or something like that - i don't have the info with me).
I've done a "chkdsk /F", a full reformat and reinstall of XP (it had 98SR2), and I found another utility that does a physical scan of the disk also. I also tried updating the system bios (it's a QDI Legend Advance motherboard).
I've tried every diagnostic utility that I could find. I tried the SISoft burn-in wizard and some memory scanner. Everything works fine. It's just that periodically it will not boot. I must shut down and restart several times before it will reboot.