External storage drive

Nothing missing. It may have one of these causes:

Windows has failed to assign it a drive letter. Do this manually in Disk Management:
Control Panel > Admin Tools > Computer Management > Disk Management
In the bottom-right panel, find the ribbon which relates to the Iomega drive (it will have no letter or drive name & may be labelled as "Raw").
Right-click it and choose "Change Drive Letter & Paths"
Click "New"
Select a letter.
Click 'OK'.

If the drive is not shown in Disk Management, it may have failed.
You can confirm this by testing it with SeaTools for Windows: http://www.seagate.com/support/downloads/seatools/