Do the followiing for a no muss no fuss installation ot the drivers:
Disconnect the programming cable from both the computer and scanner.
Download and then run this file from FTDI, the manufacturer of the chips on the cable:
http://www.ftdichip.com/Drivers/CDM/CDM%202.04.16.exe
Plug in the programming cable to your computer. You should see a notification that the cable has been found and shortly afterwards a notification that it is ready for use.
During the process the notifications will indicate which com port it is using or you can go to the Device Manager and see the port number. Make sure you are using that port number in your software.
After drivers finish installing, insert the plug into the scanner (Do not use the short adapter cable for most RadioShack scanners.)
The above will work for both 32 and 64 bit versions of XP and Vista