I'm "borrowing" a machine at work to help with my video conversion project. The machine is a dual quad-core Xeon E5520 2.7GHz with 12GB of RAM. I'm going to be converting mostly xvid/divx files to h.264. I installed Windows 7 x64 thinking that would give me my best choice of programs to use but in searching around, it looks like there aren't many options that will take advantage of the 16 logical processors on Windows (due to lack of 64-bit support). So my questions is:

What program would you recommend with this setup? I'd like for it to take advantage of _all_ the processing power if possible. I don't mind throwing Linux on there if that's what it takes.

Thanks!