Getting stop error 7e after installing XP SP3?
If it is an AMD machine, safe mode boot and disable the IntelPPM service
regedit -> HKLM\System\CCS\Services\Intelppm (Start value to 4).
Alternatively you could do recovery console and "disable intelppm"
It could also be the fault of Alcohol 120% locking the atapi.sys
Fix it and replace atapi.sys with one from sp3 and disable a347bus.sys and a347scsi.sys in windows\system32\drivers
It could also be caused by an infection that uses atapi.sys as a trojan to make a hidden filesystem.
If you are really lucky, it will be all 3!
XP sucks, Compaq sucks too. Lazy install from a base image with the wrong drivers and installing crapware in the base install.