I have had problems trying to get my HP ScanJet 3300c to work with Windows XP.
I found out that the Windows Image Acquisition (WIA) service of windows XP conflicts with my scanner software. This WIA service provides image and scanner wizards and stuff.
So the solution for me, was to disable this WIA service permanently:
msconfig [type and hit enter]
uncheck the box of Windows Image Acquisition [with a click]
Install your sj640.exe or other scanner software (find it somewhere, it's not in the zip-file)
I think this might work for many other scanner software which conflict with the WIA service of Windows XP.