I run without cdloader2. Disabling it was part of the
instructions to run without the dongle.
The dongless method stopped working last December. So, you shouldn't follow those instructions (except step #9 if you want to disable cdloader2). But, I still have cdloader2 disabled and MJ still works.
Disabling cdloader2 may cause MJ to not automatically load when you plug it in. You may have to manually start it using the shortcut created on the desktop when MJ first installed itself.
I don't know if that will resolve a drive-letter conflict. You may have to get into "computer management" (right-click My Computer, and choose "manage"). Look at the drive letter assigned to the magicJack CD drive when your real CD drive isn't connected. (And, the drive letter assigned to the real CD drive when MJ isn't connected.).
You may have to put a disk in the physical CD drive to get it to appear in the top pane's list of drives.
You can right-click the drive in the top pane of the "computer management" screen and change the drive letter.
You need to be careful doing anything in this screen. You could lose data on your hard drive if you choose the wrong drive, and wrong operation. It's always wise to create a backup if you're worried about losing data.