I had the idea that maybe somehow the game acquired a top priority ranking for usage. If you go Ctrl-alt-del -> Processes and right click on a process, then Set Priority, it will allow you to set whether a program gets preference when resources are tight.

Even though MM7 says it is Normal, nonetheless it is clearly being greedy. Therefore I suggest setting it to BelowNormal (or even Low). It won't change the CPU hogging, but it will now take a backseat when you use other programs (being of lower priority), so they should load up and run at near normal speeds.

You might notice a rare skip or stickiness while playing MM7 thereafter, but I think it very minor compared to being able to use other programs.