Need help to create subkey

I am in hopes that someone can help me with this problem. I dual boot with
Vista and XP on two of my 4 machines, I have found the workaround
information for hiding the Vista drive from XP do that it won't delete the
Restore Points, or so it says, and I have a situation I am not sure how to
resolve.

Here is the workaround in the KB article:
To keep Windows XP from deleting restore points of the volume in Windows
Vista, add the following registry entry under the
HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices\Offline registry subkey in Windows
XP:

Value name: \DosDevices\D:
Type: REG_DWORD
Value data: 1

Note If the HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices\Offline registry subkey
does not exist, you must manually create this registry subkey. Create this
registry entry when you have installed Windows Vista on the "D" partition in
Windows XP.

My Vista is installed on the E: drive in XP, so I have found the subkey,
but, the \DosDevices\E: subkey is a Reg_Binary key with different Value set
up. I have tried to create a DWORD for the \DosDevices\E: but, it says that
it is already there, although, it is not a Binary and not DWORD. I don't
know what the existing subkey may be for, so I don't want to overwrite it
unless I am sure it won't mess something else up. And, it I change the name
of the DWORD I don't know if it will work.

Any suggestions would truly be appreciated.

Jan