Distributed or grid computing question

Hi all.

I'm looking to upgrade our studio to a Mac-based system, but that leaves me with several Windows computers hanging around doing nothing. I'd find it a lot easier to justify this if they could be re-used with Compressor's distributed computing feature, so that we can process our video much faster, with less initial investment (I'd not need a 12-core Mac Pro if I could use all our dual core PCs to speed up the job)

I know that there is software out there to allow Windows PCs to act as xGrid drones, so I was wondering if anyone knew about anything similar that allows Windows machines (these happen to be running XP) to take some of the load of processing video with compressor.

Thanks for reading.
Andy.