Did you partition and format the drive after the install? It will not show in Explorer until you do.
If you have a CD of software that came with the drive - use it to partition and format.
If you got a bare drive then:
type diskmgmt.msc in your run command
You should see the drive in the graphical display on the right of the screen.
Right click the drive and a drop down menu should give you a choice to partition:
you should partition it as one big partition the full size of the drive.
Then go back and right click again and select format
after that (you might need to restart windows) you should see the drive in Explorer (My Computer)