Is there anything else USB that works with this computer ? If not, then maybe the USB drivers need an update.
Uninstall everything related to the scanner, then unplug it, download the latest driver from
www.plustek.com , then plug the scanner. When it asks for a driver, direct it to your downloaded (and previously unzipped) driver.
If I remember correctly, Plustek scanners ask for a serial number located on the scanner's back when it installs, so type it right.