External USB Hard Drive not showing in My Computer but is in Device Manager

Another useful old post. I actually run into this quite a bit, so have a shortcut to Disk Management on my desktop:

Heehee...this one made me feel like an idiot...I bought a 120 G External USB HD, & connected it to my laptop. For some reason it wouldn't show in My Computer. This perplexed me since I could see the drive in Device Manager & everything looked ok. Then I noticed the drive letter it was assigned - G:

Hmmmm...same as one of my mapped drives set to reconnect at logon. Duh...problem solved - assigned my mapped drive a different letter & voila (or viola as some would say), I could see my drive. That was 20 minutes of my day wasted, but at least it provided me with a bit of humor.

http://techrepublic.com.com/5208-6230-0.html?forumID=102&threadID=239428&start=0

How to reassign a drive letter:
To change an existing drive letter on a drive, on a partition, or on a volume, follow these steps:

1. Log on as Administrator or as a member of the Administrators group.
2. Click Start, click Control Panel, and then click Performance and Maintenance.
3. Click Administrative Tools, double-click Computer Management, and then click Disk Management in the left pane.
4. Right-click the drive, the partition, the logical drive, or the volume that you want to assign a drive letter to, and then click Change Drive Letter and Paths.
5. Click Change.
6. Click Assign the following drive letter if it is not already selected, click the drive letter that you want to use, and then click OK.
7. Click Yes when you are prompted to confirm the drive letter change.

The drive letter of the drive, the partition, or the volume that you specified is changed, and the new drive letter appears in the appropriate drive, partition, or volume in the Disk Management tool.

http://support.microsoft.com/kb/307844