Windows, Linux or what to install

Hi there

I have four:
Intel(R) Core(TM)2 CPU 6300 @ 1.86GHz [Family 6 Model 15 Stepping 2] (2 processors)

And I want them to run seti@home.

What OS is the best for this? I have now win xp pro sp3 and Ubuntu 10.4. It looks like win is fastest. I use this utility to make it faster http://lunatics.kwsn.net/index.php.

Is it possible to make then running faster?

Thanks
Nenad