When upgrading to windows Vista I found out that my, USB connected, HP Scanjet 5370C scanner isn’t supported by windows Vista anymore.
After google-ing this issue, I found a post from ‘Frank’ with a working solution.
Goto http://www.hamrick.com/, download the trail version of Vuescan. Install this program. Open device manager, select the HP Scanjet device and update the driver. When asked for a location, point to the install folder of Vuescan (eg c:Vuescan) and the driver is installed. You can test the scanner with the trail of vuescan.