The only way a windows cluster is even viable is if they're connected via gigabit ethernet. otherwise it's such a bottleneck you'd not realize much, if any, speed increase.
There used to a setup years ago, in which there was 2 motherboards in one box. But one was an Apple board, the other a PC. If I remember right, it booted off of the Apple side then you could boot the PC environment from inside of the Mac OS and use them simultaneously. Kind of like virtual PC, but with true hardware, no emulation. Neat stuff. But not exactly what bogykrk was asking, I know. Remember, you're unique... just like everyone else.