Hi Ed,
Are you perhaps thinking of the "Recovery" partition?
On many systems this partition is Drive Letter "D".
The Recovery Partition is not a partition to which you should be adding any files or folders. The only data that belongs in that partition are the Recovery files created by the system for the purpose of restoring your computer should it be necessary.
Example - File Explorer (Windows Explorer) window showing the contents of the Recovery partition
NOTE that in the example, there are a number of USB drives and an external drive shown and blacked out.
If you are indeed, asking about the Recovery Partition, below is some information about it:
HP Notebook PCs - Removing the HP Recovery Partition - c00810279
If you need access to the Recovery partition, you can access it from an account from an account with Administrator privileges. If you are using an account with the appropriate privileges and you see the warning that you need permission to continue, in most cases you can click through the message and gain entry.
If you are using Windows 8, good news: File History backup is flexible, easy to use. The backups can be stored on a USB drive, an external disk, even a NAS system.
HP PCs - Backing Up Your Files (Windows8)
Extra Details on File History are available in
Windows 8 Features – A Quick Tour
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