I was able to modify the
Epson Perfection 2400 Photo driver to work with my 1640SU under Windows 7 x64.
Here's the driver:
Epson America, Inc. - Downloading File Page
Open it with 7-Zip (or whatever you use), extract the file named
_winzip_, extract the files contained in
_winzip_ using 7-Zip (or whatever you use).
Open
Es27.inf and replace all instances of
USB\VID_04B8&PID_011B with
USB\VID_04B8&PID_010A and save and close the file.
Now go to the Device Manager, right click your scanner, Update Driver and Software...
Browse my computer..... and use the folder you extracted
_winzip_ (with the now modified
Es27.inf) to.
That should do it, worked great for me.