If I follow every thing in this thread I think the OLD COMPUTER RULE APPLIES (old rule not old computers) Turn on ALL accessories first and then boot the computer. My HP6300C doesn't have an obvious on off switch. The switch it has blocks the accesibility of the power cord and also locks down the scanner head. The scanner does have to initialize before the computer looks for it or it won't be found. If the scanner is running off the USB port unplug it (wait a little while) and plug it back in. If you get a message that new hardware has been found I think something is wrong. what I don't know. other wise the computer should recognize the scanner and run normaly.

Paul