You didn't say which version of Windows you're using.

Acer's scanners are now supported by BenQ. Imaging Device Drivers

You can also find your Installation Manual for WinXP here in .pdf format. It says to set the SCSI ID to 2.

Normally, you should be able to set it up for any address except 7. That is usually reserved for the SCSI Interface itself.

Hope this helps out...Good Luck!