We have a USB connected HP CM1312nfi multifunction machine connected via USB to a Toshiba laptop running Windows 8.1. Everything was working fine, scan and print, until I needed to attach USB hard drive to copy some files. Under the users domain log-in (which has full administrator rights on the local PC) the external drive was not recognized. I switched to a local machine account and was able to access the external drive.
When we plugged the multifunction back in and tried to scan we got a Scanner Not Found error. After several attempts to get the system scanning again (including a re-boot) I deleted the printer and scanner from Devices and Printers, removed the drivers from the Print Server and uninstalled the HP software for this printer.
I then attempted to re-install the latest software and drivers (same source as used for initial install). No matter what I did the installation would hang when it asked to plug the printer in via USB. To confirm this was not a hardware issue with the printer I went through the same steps on a different laptop of the same make with Win 8.1. On the second PC an un-install and re-install went fine and I was able to print and scan with the same printer.
During a final attempt to install I noticed that when I plugged in the printer (when prompted by the software installer) an External Disk named CM1312 showed up. This "disk" can't be accessed; says it has no media, but it shows up in File Manager as well as in Device Manager (as both a Removable Disk and USB Device).
I suspect that somehow windows got confused and registered this device as a drive and that's why the HP software can't see it being plugged in. What I can't figure out is how to break this association so that it will be seen as a new device.