Currently Being ModeratedAug 20, 2012 1:23 PM (in response to Grace30318)
Not all USB printers are compatible at the USB port of the AirPort Express...and Apple does not provide a compatibility list....so this is one of those situations where you won't know if something will work until you try.
Connect the printer to the USB port and power up the printer
Open System Preferences (gear icon on the dock) on your Mac
Open Print & Scan
Hopefully, your printer will be recognized
If it is, click it to highlight it
Try to print. Be sure to choose the correct printer in the print dialog box. If you have connected the printer to your computer in the past, it will appear as if you have the same printer installed twice on your system.
Closer inspection will reveal that you a printer installed on your Mac and another installed at the AirPort Express.
Choose the AirPort Express location when you want to print.