When you mount a drive to an empty folder on the NTFS file system, you are not subject to the 26 drive letter limit, as mounted drives use drive paths. You could move My Documents to another drive and them mount is as C:\My Documents, increasing the size of your C: drive.
NOTE: DO NOT mount a volume on a cluster server.
To mount a volume at an NTFS folder:
- Create an empty folder on an NTFS drive, like c:\MyFolder.
- Right-click My Computer and press Manage.
- Press Disk Management.
- Right-click the volume to be mounted and press Change Drive Letter and Path .
- In the Change Drive Letter and Paths for dialog, Press Add .
- Select Mount in this NTFS folder and type the path of the empty folder (c:\MyFolder) or Browse. Press OK.
When you unmount a volume from an NTFS folder, Windows removes the mounted volume, but leaves the folder in place. To remove a mount point from a volume:
- Use Disk Management to right-click the NTFS volume to be unmounted, and press Change Drive Letter and Path .
- In the Change Drive Letter and Paths for dialog, select the mount point you want to remove and then press Remove .
- Press Yes when prompted.