Setting CPU cores off-limits to all threads not specified (preferably in Windows 7)

Solution 1:

Well, talking about shotgun solutions, I think you should go the script way using, as an example Command Line Process Viewer/Killer/Suspender for Windows NT/2000/XP and write a script (any language accepted) that would take all active processes (excepeted the one of your choice) and set their affinity to any other processor than the chosen one. However, as it is only an affinity, I can't ensure you that your processor will be left alone for your preferred program.

Personnally, i consider the optimal solution to your problem is to set both affinity and priority.