Now, I finally found the solution and just wanted to write it down in case I (or anyone else) should ever need it again. The solution was found on this page and said:
XP asks for drivers or just want to install new hardware
XP comes with drivers for USB mass storage. If it asks for drivers then it has forgotten where they are...
Start the Registry Editor (Run -> Regedit). Check if under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft
\Windows\CurrentVersion the item 'DevicePath' points to '%SystemRoot%\inf'. Additional items, separated by semikolons, are ok but '%SystemRoot%\inf' has to be one of them.
Then delete the file C:\WINDOWS\inf\infcache.1 - XP will recreate it.
Another thing to check is if the values 'FactoryPreInstallInProgress' and 'AuditInProgress' are set to '1' under
. They should be 0 or non present.
Although this was written for Windows XP, it worked on Vista. Specifically deleting C:\WINDOWS\inf\infcache.1 was what made the trick for me.