First of all, run an antivirus program directed at the external drive, to make sure it's clean. You may have done that already, but didn't say whether you ran your antivirus against the system drive or this drive, or both.
Next connect your (?USB or SATA or Firewire) external drive to your clean computer, and go to Disk Management, to see if it is recognized by your OS (Win-7, Vista, Win-XP ??)
Go to the graphical area in the lower half, and list for us what it says in the Drive Status box (left side) that starts with Disk 1, Then in the Volume Status box just to the right, list the color of the band above it, and what is says, such as VolName, disk letter, size, NTFS, Healthy, or whatever it lists.
That way the folks will know if it is active, and partitioned still, and if there is a file system still on it.