If the external hard drive does not appear in Windows Explorer, I suspect it isn't OneCare, but an overlapping drive letter designation conflicting with a mapped drive or the drive is unformatted.
Open Control Panel, Administrative Tools, Computer Management, Disk Management (under Storage) and your physical drives will be displayed.
The removable drive will appear in this list and will show the assigned drive letter and the format and status of the drive.
You can change the drive letter to one that is not used by a Drive Mapping that has been configured for a Network Share and you can format the drive from here, too.
Once you've changed the drive letter, you'll probably want to correct the OneCare backup settings as follows:
Open OneCare
Click Change Settings
backup tab
Click change settings in the lower left
Make sure that the first screen for Centralized Backup has "No Centralized backup" selected
Click your PC on the left.
Uncheck the selection for "Turn on backup for this PC."
Click Next and save the revised plan.
Go back to the backup tab and click Change Settings in the lower left once again.
Select your PC and click.
Click Turn on backup
Select the change location link and select the drive you want to use for backup
Modify the schedule as desired for "When"
Select the file types as desired for "What"
Click next and save the revised plan with the new selection.
Please let us know if this fixes it for you.
-steve
