Several weeks on this.....

Xp SP2 Only.

Select F8 on boot to switch off the automatic reboot.

Run and wait for the reboot but......

You will then see the error on the blue screen....

DRIVER_IRQL_NOT_LESS_OR_EQUAL

and the killer

Atapi.Sys

Check the microsoft database but ignore the suggestions only if you are mad like me....

Search for Atapi.sys in the C:/windows driver folder.

Delete it (keep it in your waste bin just in case).

No warrenty implied and keep them backup disks close....