I had a similar problem and the following worked:
A.Right click the Computer or My Computer icon and select Manage.
B.Click the plus (+) sign next to Storage if it is not already expanded.
C.Click Disk Management.
D.Right click the icon for the Hard Drive and click Change Drive Letter and Path.
E.Click the Edit button
F.Next to Assign a drive letter, select an unused drive letter from the drop-down menu.
H.A message appears that states 'Changing the drive letter of a volume may cause programs to no longer run. Are you sure you want to change the drive letter?'
J.Restart the computer. (Not always necessary)
K.Double click the Computer or My Computer to see if the Iomega Hard Drive is detected.