Well I was able to install SP1 on my HP tx2051 with Vista Ultimate. I had to update the Windows Defender definitions first and then manually check for updates. The download was 121 MB. It took a while to download and installed in 15 minutes. After the install the computer restarted and finished installing the update.
I tried to install SP1 on my Gateway CX210X but it would not show up in Windows Update. I think it may be the sound card driver. Vista SP1 has some known compatibility issues with certain drivers. I checked for updated drivers both nothing was shown. Hopefully this will be resolved soon.