My Computer Doesn't "See" External Hard Drives

Type Computer Management in the search box next to Start Button. Click on Computer Management in the results. On the window that opens click on Disk Management. It will list all drives. Find your external drive in the lower section. I'm assuming no drive letter is assigned or it has assigned a letter thats already in use by something else (happens often). Right click on the drive and select change drive letter. Enter a new unused letter. Hopefully that will fix things.