You can do this using the printer pooling built in to Windows provided both printers are the same make and model. To enable printer pooling select “Devices and Printers” from the Windows start menu then right click on the first printer and select “Printer Properties”. Next click on the “Ports” tab and select the “Enable printer pooling” checkbox. Then select the other printer in the list of printer ports. The printer properties window should look something like this:
Click OK and then repeat the process to enable printer pooling for the second printer. Once setup, selecting File->Printer Setup… in the photo booth software should look something like this:
The “Where:” section should list the USB ports for the two printers (e.g. USB005, USB004). Windows will now treat the two printers as a single print queue and will send print jobs to the first printer if it is available or to the second printer if the first is busy.