Hi,
Sounds like a simple case of windows not automatically assigning a drive letter. I'm guessing your running windows 7?
If so:
Open Computer Management by clicking the Start button , clicking Control Panel, clicking System and Maintenance, clicking Administrative Tools, and then double-clicking Computer Management. If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
In the Navigation pane (on the left), click Disk Management. You should have a disk without a letter, right click and then you may need to click make partition active, then assign a drive letter.
It will now be accessible from my computer.
Hope that helps
Mark