First get your Printers IP address.

Make sure that the printer is connected to the Airport Express and turned on.

Start > Control Panel > Devices and Printers

Add a printer > Add a local printer > Create a new port:Standard TCP/IP Port  > Next

Hostname or IP address = your printers IP address

In the Port name field, add “IP_” before the IP address (without the quotation marks)

Check the box “Query the printer and automatically select the driver to use” > Next

Windows will take a moment, then it will require Additional port information

Choose Custom > Next

Choose your printers driver. If it is not listed, try Windows Update or Have Disk > Next

Enter a Name for your printer > Next ***(I choose to include in the name, that this printer is on the AirportExpress, this helps differentiate between the printers when plugging in the printer via USB)

The printer will begin installing…

Check “Do not share this printer” > Next

If you want, you can check the box to set the printer as the default printer

Try printing a test page > Finish