Cannot modify partition backup target

I originally created a partition back to a USB drive connected to my Windows 7 computer. I then changed the USB drive connection to another location (network share and a mapped drive). I could not change (edit) the location to do a new partition backup. When I changed the target location (I found the new mapped drive in the destination drop-down) and clicked OK I received an error that the original location could not be found. Problem of course is I no longer am using the original location and was attempting to change to the new location. Finally, in frustration, I removed the partition backup from the Backup and Recovery window so I could recreate from scratch but now cannot create any new partition backups. Clicking "Disk and partition backup" only appears to allow me to create a disk backup, never a partion backup.