USB device drivers "forgotten" when I use my laptop away from home..

I'm having some strange problems with WinXP (SP1) forgetting USB
devices. I've got a USB mouse (MS Optical) and a USB soundcard
(Soundblaster Extigy). When my laptop is on my desk and remains
hooked up to the USB devices, everything is fine. They're
automatically recognized on bootup. If I use my laptop somewhere else
(without the USB devices) and then come back here and hook everything
back up.. lo and behold, WinXP has totally forgotten that they ever
existed and I have to reinstall the drivers. Luckily, all of the
drivers files are still sitting in various Windows directories (mostly
/system32/), so I just have to track those down. It's pretty
annoying, though, having to always do that after using my laptop away
from my desk. It's especially strange since all of the necessary
files are sitting right there for WinXP to grab.

Has anyone else had similar problems? If so, how did you get WinXP to
automatically recognize USB devices afterward? Any help would be
greatly appreciated! Thanks..

-danny
bluecalx@yahoo.com