[SKI]

I think your problem is you are looking for a simple fast easy solution.
Nothing wrong with that but rarely the case with PT.

You were far to willing to buy a new processor, hard drive and ram instead of trying to find a culprit.
The i3, 4G and 1 hard drive is not optimal but not prone to locking up, it would more than likely give you performance issues prior to reaching that point.
Granted the things you purchased will benefit you once your system is up and running properly so they still are beneficial.

You said only PT and even sometimes shutting down PT correctly gives you a blue screen even after re-installs.
So I would look for the problem to be more PT based.

As benherron.rrr mentioned the optimizations can choke some systems because of how the manufacturer implements something so never overlook them as a problem.

Download something like Reaper and install it on your computer.
Try using it with ASIO4ALL and your built in sound.
It it plays and records ok then try using Reaper with the mBox as your output.
This will at least let you test your system performance and then your mBox performance.

If it passes these 2 test then it would seem to be related to your PT install, how you are installing it or something you have installed that is conflicting with PT.