I think PRE 3 (with the 3.0.2 patch) was the first to run under Vista. No version of PRE is currently stated to run on a 64-bit windows system, although many (including myself with PRE7) run it faultlessly on W7-64.
If you have W7 Professional or Ultimate you could see if PRE2 runs in XP Mode (check Microsoft downloads for the XP Virtual Machine). You could also convert your W7 machine into a multiboot system (where you select at start up if you want to run W7 or another Operating System you install on your machine. The Internet has plenty of guides on how to do this.
Insanity is hereditary, you get it from your children
You may also want to check on Amazon.com and eBay for a copy of version 7. (Just make sure it's a legitimate copy.) You can probably find it for a fraction of the cost of the current version -- and you may even be happier with its performance!
I have been reading some reviews on PE8 since I posted this. The
reviews look pretty bad.