[Jmo9]

Thanks for taking the time to try and help.

I tried everything as suggested:
-disabled audio devices other than Mbox
-shut off all windows sounds
-disabled host control in Mbox

The only thing I couldn't do was power up the Mbox before PC because Mbox is powered by PC.

Unfortunately, the problem wasn't solved. I got this new message:
The selected ASIO audio device could not be initialized. Please choose another audio device.

It gave me no other audio device to choose from.

I tried to do a "win optimization". I wasn't exactly sure what you meant but I did an msconig, and shut down everything (non Microsoft) on the services and startup and enabled only Avid programs (there were only two: Mbox audio device manager and Digidesign MMERefresh).

This also failed to solve the problem.

I noticed as PT is booting, the awful noise always starts as it says it is: setting up peripherals, initializing machine control. Not sure if that information helps.

So. I'm still looking for other ideas. I'm very appreciative of all efforts to help. Thanks.