At the Command Prompt type the following and press "Enter": mountvol D:\ /D Close the command prompt. Drive letter D: should now be unused and available.   Here is some info on Mountvol, it is very powerful be cautious using it: [URL] 
I'm just going through the process of personalizing a new Inspiron 14z with Windows 8. The one thing that has me stumped are all the partitions that ship installed on the drive, due to a combination of everything being different on Win8, Dell doing things their own way, and GPT formatting.  Generally I would like to know what the heck all those partitions are for, but it's fine if that will be a slow learning process.  Specifically and immediately, I need to change the drive letter assigned to the "WINRETOOLS" partition.  Currently it's D:, and the problem is that for 10 years I've been using D: as my data partition, and quite a  number of applications, configurations, settings, etc. assume that all my files are on D:.  For instance, by having all my music on D:, I can sync iTunes library and preference files between machines, and all ratings and playlists match from one machine to the next.  Same thing for my photos.  Same thing for a bunch of utilities like FTP consoles, sync utilities... In a prior version of Windows, I would just go into Disk Management, right click the partition in question, assign a different drive letter, and job done.  On my machine, the 2GB WINRETOOL partition doesn't even show as having a drive letter in Disk Management, despite the fact that it's D: in Win Explorer.  Additionally, the only right click option is "help".  I've taken that option, and, despite its aspirations, it's not helpful. How can I change that drive letter to something else?  Should WINRETOOLS even have a drive letter in Explorer (some posts I've seen indicate that it should be hidden)?  If I do manage to change the drive letter, will that break its function, whatever that is? .... My machine has a 500GB spinning disk, which has all the aforementioned partitions.  I've shrunk the C: partition to 80GB, in preparation for creating a data partition.  I have not yet formatted the unassigned space as I would like to solve this WINRETOOLS thing first.  Finally, there is a 32GB SSD that I've set up as an Intel Smart Response cache, and it's no longer visible to the OS.  
How can I change the drive letter assigned to the "winretools" partition on a 
Win 8 laptop?