
I did another clean format and reinstalled windows.
I installed scope, and then ableton.
Tested the stability using the scope midi in/outs >2000 bars no crash. satisfactory
Installed the MOTU drivers.
Tested again with scope midi in / motu midi out -- it crashed at ~180 bars.
So there was a problem with the MOTU.
I checked my IRQs there was a conflict with the onboard ethernet and onboard audio with a USB device. I turned off the onboard ethernet and onboard audio in my bios.
Tested again with scope midi in / motu midi out -- it crashed at ~310 bars.
A little better, but not good enough.
I then added the DisableSelectiveSuspend key to my registry.
Tested again with scope midi in / motu midi out -- no crash at > 7100 bars ~ 3.5 hours.

The difference between this time and the previous clean install is that on the first try I installed drivers for a pci ethernet connection, installed anti virus software AVG and a firewall Comodo, and then fully updated my windows.
I would turn off the net connection, the firewall and the anti virus before testing in ableton, but somewhere along the way something was changed or something unhappy was added that gummed up the system.
I'll keep this install a net virgin (As I know you should keep your DAW off the web) and do internet from an old win2k partition.
Now that it's working, I'm a bit less inclined to upgrade, even though my system is pretty old, as long as it's running what I need I'm happy and the longer I wait to upgrade the exponentially better the next computer will be.
thanks again everyone, there were numerous problems that needed to be fixed and each of you gave advice that was essential in the end.
woot! to planetz!