Hi, there is something you might like to try, will do no harm follow this:-
1. Open a Windows Explorer window by right clicking on Start and
then clicking on Explore.
2. In the address bar, type C:\windows\inf and press Enter.
3. Find and then right click on the file named INFCACHE.1.
4. Select Properties.
5. Click on the Security tab.
6. Click on Edit to edit the permissions of the file.
7. Click on Add to add User Groups.
8. Type Administrators in the User Groups field and click on OK.
9. Set Administrators to Full Control and click on OK.
10. Move or delete the file INFCACHE.1.
11. Reinstall a device to force Windows to rebuild the INFCACHE.1 file
(DO NOT reinstall the same external hard drive that you were having
issues detecting before. Please connect another USB device other than
the one that Vista had an issue detecting).