Beowulf – Windows Cluster

Hi everyone.
I keep accumalating “old” – 3GHZ machines and all theyre doing is sitting in my basement. I was thinking of setting up some sort of beowulf system, but all Ive found is based on linux and I preffere to keep the system user friendly. Does anyone know if/how it would be possible to run this system under windows?

My Goal would be to have n slave nodes, and anyone could come up, plug their laptop into the network, run a batch, and be connected to the “collective”. I know its pretty mad, but any ideas?

Cheers