|Seems this problem is usually caused by HP driver installs (a printer or something)|
If the customer has any of these, close the popup with ctrl-alt-del. Uninstall the driver, reboot, temp. switch off User Account Control in the security panel (if you have vista) then use the driver disk again: it should sort it.
Did the customer run any installs from a memory key? This could explain the missing drive.
You can also try Windows Installer CleanUp Utility scroll down the following page to find it (plus some blurb about it)