If youv'e encountered a problem where Windows Vista (and maybe XP but im not sure if this applies) can locate the driver for new hardware automaticly when you plug in then there are 2 possible causes.
1. Incorrect settings in Control Panel
Go Control Panel\System and Maintenance\System click on Advanced System Settings > Hardware > Windows Update Driver Settings and select 'Check for Drivers Automaticly'
2. Corrupted infcache file
Go to %systemroot%\inf and find infcache.1 open the proporties and click security, grant yourself full permisions. Then rename the file to something harmless like backupinfcache.1 or delete it.
This has worked for me and a few other people but that dosn't mean it's safe or will work. Do this only at your own risk and not mine.
Have a nice day.