I am pretty sure its also required on Vista as well and on Vista I think you actually have to have a monitor or a vga dummy connector to make vista think you have a monitor connected by putting a load onto the card.
You will need a vga test/dummy connector which is very easy to make just need a hd15 connector and 3 75 ohm resistors you could also just use the dvi to vga adapter and insert the resistors into that as well.
Here is a link to the FAH folding Forum about it http://foldingforum.org/viewtopic.php?f=52&t=4864
And a link showing how to make a dummy connector
http://soerennielsen.dk/mod/VGAdummy/index_en.php
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