WinXP Professional work very well!!Two processors make rendering faster. And no you don't have to use the batch renderer to utilize both processors, as long as they are in the same machine. Just tell Maya how many processors you want it to use when rendering, and that's it. Pretty simple. At least that's how it is on my DP unit using Maya for OS X. I don't know how it works on PC's, but I'm sure it's the same.