MicroCode Studio works just fine with Windows7-64.
That's what I have at work.

When installing, be sure to Right-Click the install program and "Run as Administrator.
Even if you are logged in as an administrator "user".
Don't let it just AutoRun when you put the CD in.
It needs to write several Registry keys that requires a higher permission level than some computers are setup for..

PM.exe, the default assembler that comes with PicBasic Pro is a 16-bit program.
It will not run on a 64-bit system (except in a virtual XP).
So be sure to use MPASM for the assembler stage.