The main reason for Expose is because OS X doesn't have a taskbar for you to easily find a certain window - considering XP has a taskbar there's not really any reason to need Expose. Anything you may find will be a cheap ripoff though.
I have tried one of those versions out there some years ago (I had to work with a Windows PC), but the implementation was horrible even on a highly specced PC. It lagged like hell.
You could have a look at the Hackintosh route. Use MRoogle for searching this forum for various threads about that.
No need for all that. I have to use a XP machine at work, but often find myself missing Expose. If I could install any apps, I would install something that gives me that feature.