We are trying to install an business banking application (XP vintage software) in Windows 8.1 Pro but it cannot see the mapped drives.

Hi,

As my understanding, you encounter the issue that the mapped drive doesnt appear in you Windows 8.1. If there is any misunderstand, please help to clarify.

For this issue, we can try following steps to check the results:

Step 1: Disable Fast startup in Windows 8.1 and restart computer.

How to Turn "Fast Startup" On or Off for a Hybrid Boot in Windows 8 and 8.1

http://www.eightforums.com/tutorials/6320-fast-startup-turn-off-windows-8-a.html

Step 2: Lets try to map this driver again via command line:

How to Map Network Drives From the Command Prompt in Windows

http://www.howtogeek.com/118452/how-to-map-network-drives-from-the-command-prompt-in-windows/

If the issue still persists, please try to install the latest network adapter driver from manufacturer website to see whats going one.

In addition, I recommend you check the compatibility of this app on Windows 8.1 compatible center. Since the incompatible app may cause many issues on your current system:

Compatibility Center

http://www.microsoft.com/en-in/windows/compatibility/CompatCenter/Home?Language=en-IN

Hope these could be helpful.