In order to use a scanner that utilizes a USB connection (as opposed to SCSI), you must install both the ISIS driver and the TWAIN driver. The TWAIN driver is used by the Windows operating system to detect the scanner through the USB connection. The ISIS driver is then used by PaperFlow for scanning.

Not all USB scanners have an ISIS driver available. If you go to http://www.scannerdrivers.com and select your scanner from the list, it will show what Interfaces are supported. If USB is listed, then there should be an ISIS driver available for that scanner using a USB 1.0-2.0 connection.