The Drive letter subkey represents a disk drive that the system recognizes.
To map to a network drive, from the Tools menu select Map Network Drive. In the Folder box, type the path to the drive, and then click Finish.
The Drive letter subkey is a variable representing the subkeys under the HKCU\Network key. It does not actually appear in the registry. This variable entry displays information that is common to the subkeys under this key.
The subkeys are named for the drive letter to which the drive is mapped. The system adds a Drive letter subkey to the registry when a drive is mapped and Reconnect at Logon is selected. The entries in the Drive letter subkeys store data that is used to reconnect the drive.