Below steps will show you how to hide a drive in windows 7 by removing it’s drive letter,of course you can use the same way to assign it a drive letter again if you want to access it’s data again.
1.Right click Computer and click Manage
2.Select Disk Management from the left pane
3.In the right pane,right click the drive you want to hide and select Change Drive Letter and Path…
4.Select the drive letter then Remove it(Click Yes when a warning prompted)