At work, I got a Thinkpad T61p with Vista Ultimate for my computing needs. Unfortunately Service Pack 1 would not appear in Windows Update. No updates were available through Lenovo System Update.

Reading the release notes from Microsoft led me to suspect the fingerprint chips driver was the culprit. A quick visit to Upek (producer of the chip) led me to updated drivers, and presto! after a couple of reboots Service Pack 1 appeared in Windows Update. Nice