Quick note here for those that might be in need of help with Vista Service Pack 1 . . .
1) If you have not yet installed it, make sure you have the latest device drivers installed for your video and network cards before installing SP1. There have been reports of some people being greeted by a black screen on reboot after SP1 was completed - because their video driver was not compatible. The only solutions in that scenario are a complete clean re-install from the Vista Bootable DVD, or installing a new video card for which Vista has native support.
Among other guilty devices; the embedded graphics card on certain Intel 945 chipset motherboards seems to be causing this problem for people that did not first upgrade to Intel's latest driver before installing SP1.
Same goes for certain embedded network cards, leaving you with no easy way to download a newer driver after SP1 is installed. There's always sneaker-net of course.
2) If you have installed it and are having trouble, here is the "super secret" direct support page from Microsoft - which includes free phone support. Super Secret because they are not advertising the fact that they do provide free support to any legal owner of Vista trying to install SP1.
By "any legal owner" they include full retail purchases, upgrade versions, and now all OEM versions.
Here it is: https://support.microsoft.com/oas/default.aspx?ln=en-us&prid=11274&gprid=500921