I've misplaced my "discs" for Photoshop CS3 and its installed on my old XP 32 Bit machine. If I copied it out and placed it into the correct folders on my Windows 7 64bit, will it work or is there the whole Registry thing in the way?

Try and find out.

 

Might as well get rid of it and upgrade to CS5.

My guess is maybe, but probably not. This is a situation where I would think that software piracy is morally right.

Yes, it should (according to microsoft). (you could always "buy" CS5 ;P)

Source

 

The registry thing you're talking about: most programs only put keys in the registry so you can uninstall from the control panel > add and remove programs, so you'll have to live without that. You'll also have to manually place a shortcut in the start menu etc.

 

I've got exactly the same problem as you, transferring from WinXp 32bit to Win7 64bit, and it's going to be a complete pain >.>