If the drivertest crashes, Mach won't run properly (if at all). Read the manual about the special driver you might need to try.
It's in the first section about installation.
If that doesn't help, you might want to turn off ACPI in the bios. This sometimes requires reinstalling XP.
I'd also try running windows update and getting all the XP updates before installing Mach3.
There's an optimization list that you can try, but usually should be the last resort.
You did reboot XP immediately after installation, right?