I assume 'E' is the CD drive. My uncle got the same error, because QB won't backup files to a CD drive. My uncle thought it was something wrong with his brand new external CD burning drive, but it wasn't. It's just a "flaw" in QB. You'll have to "backup" to a folder on your C drive and then burn that folder or the files in that folder onto a CD. That's the "workaround" to the "flaw".
I have been using their program since it was in the DOS version (for at least 16 years now). You would think they could get with new technology. If I am finally getting new technology, they should be compatible too...LOL