The iConcepts Music Express software doesn't have any restriction regarding the numbers of MP3 Players that you can use. If the second device is not recognized, press Windows + R key combination, type devmgmt.msc and click OK. Expand the Universal Serial Bus controllers list, right-click on the driver and select Uninstall. Reboot your computer, connect the second MP3 Player, press Scan for hardware changes icon from Device Manager and wait for Windows to retrieve the drivers. After that, launch the software and check if it recognize the device. If not, try uninstalling iConcepts Music Express (Control Panel > Uninstall a program) and then installing it again. If it still doesn't work, try other similar software like MAGIX Music Manager or MP3 Player Utilities.