If data computation can be "vectorized" then could work, but isn't an automatic recompile, you need to modify your program to use the SPUs.
I've read something about Cell programming on the IBM developerworks pages, but i can't find it now, anyway you can start from their "homepage":
http://www.ibm.com/developerworks/power/cell/
P.S. i've noted only now that you don't own a PS3, so i think you have better options to try first before buying a PS3, don't know about windos but for common distributions (like Debian, Fedora, Slackware) or Free/Net/OpenBSD there are tools to exploit networked PC with "little" effort, like Boinc (Berkeley Open Infrastructure for Network Computing), MPICH (Message Passing Interface) or PVM (Parallel Virtual Machine)...