The best way to take care of this is more than likely going to be finding the device in Device manager, uninstalling it, and then connecting and letting Vista reinstall the necessary drivers.
If you can do this on your own, then I suggest the following:
Open Device manager, plug in the device, find it in device manager, open its properties page, unplug the device, from properties page uninstall the device, and if prompted if you want to remove the driver completely check the box (meaning yes), then reboot your machine, log in, let everything settle down, then plug in the device again.
Key step is to uninstall the device in device manager after unplugging the device (so it won't confuse Vista anymore than it already is). However, this may make the properties page disappear, and if so, we'll need another method to get to it.
If this is not something you can easily do by yourself (or if the properties page disappears when you unplug the device), please answer the following question to start the walkthrough process:
What is the model number of the USB drive that the laptop cannot seem to access?