Acer 640U Scanner
Acer (Now known as BenQ)
Driver Date & Version
Acer 640U scanner is a flatbed scanner with USB connectivity from Acer, now known as BenQ. The latest driver version 4.03 U10 is supported by Windows 98/98SE, Windows ME, Windows 2000 and Windows XP.
For MacOS X user, they are out of luck because Acer only provided support for MacOS 8.6 up to 9.4 for 640U scanner.
Download Acer 640U Scanner Driver here.