Where he checked is valid, and has been for many windows versions as well.

I'm guessing your not seeing SP1 as an option in Windows Update due to what AndrewT was talking about.

Quote:
Windows Update will recognize PCs with known problematic drivers and postpone downloading Windows Vista SP1 until the PC has updated drivers or other applicable updates.


While SP1 can be installed manually, I'd highly recommend waiting till Windows Update does whatever voodoo they think is necessary for your machine. Of course it would be nice if there was some way of knowing what driver it doesn't like, but we all know how MS enjoys trying to simplify things to the point of uselessness.