Is the E: drive your CD/DVD burner?
Have you backed up before?
Is the CD/DVD an RW type disc? If so, try using a regular R type disc. OneCare backup doesn't play well with RW discs, especially if they have been used before and erased.
It is also possible that some other software is holding the drive. If you are using DirectCD or OnCD, which are the packet writing components of Roxio and Nero, you should uninstall them or disable that component as it may be conflicting with the drive's use by OneCare.
You can also contact support for help with this issue.
How to reach support (FAQ) - http://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/30400b52-7f26-4ba0-bc18-17e305329d90
-steve
Microsoft MVP Windows Live / Windows Live OneCare, Live Mesh, & MS Security Essentials Forums Moderator
