Steve wrote:[color=blue]
> I have a SanDisk 16gb cruzer that is easily recognized in my XP Pro
> machines and was for a brief while on my 2 Vista Ultimate machines.
> A few weeks ago, my 2 Vista Machines stop recognizing it. If I go to
> device manager, I can see it listed as a disk drive. To get it to work
> I scroll down to USB Mass Storage Device and disable/enable it and it
> pops up and all is good. If I look in Computer Mgmt /Disk Mgmt, it
> shows up as unallocated so it does not get assigned a driver letter.
> If I boot the PC with the usb drive inserted it works fine. I called
> Sandisk technial support and they said it was "Vista problem" because
> the drive works in XP and in a friend's computer also running Vista.
> Can one delete all USB devices in Vista without doing a complete
> reload of Vista. Maybe setting all USB paramters back to that after a
> clean install would help ?
> Any help would be much appreciated. Steve[/color]

Try this. Worked for me.

[url]http://www.online-tech-tips.com/computer-tips/usb-device-not-recognized/[/url]

It may not be the problem you're having but worth a try.