That option doesnt always work, or matter.
This was due to a bugcheck in XP, on this system.
I unticked that option and it still rebooted. I then
found out what caused it..
A BIOS update was somehow clashing with Hyperthreading on my system.
Rebooting the
system, and also creating disk read errors in Event
Viewer. And also raising the CPU to 43 degrees,
whereas the old BIOS only took the CPU temp to
32-33 degrees.
So, I flashed the BIOS back to the previous
working version of the BIOS. And everything appears
a OK now.