You need to check that whether the scanner is compatiable with windows Vista or not.
If yes download the drivers for win vista for the scanner.

You have not provided the make and model number of the scanner otherwise i could have checked the same for you.

You may go to the manufacturers website of the scanner and you should get all this info there.
If you have any trouble provide me with the make and model number of the scanner.

Hope this helps

Regards
Sammy