Citrix MetaFrame Application for Windows 1.8 Administrator's Manual page 35

Drive letter Is accessed from the ICA session as:
Client Drives:
A A
B B
C V
D U
Server Drives:
C C
D D
E E
If you do not want the MetaFrame server drive letters to conflict with the client
drive letters, the server drive letters can be reassigned to higher drive letters. If the
server drives are reassigned, user sessions have the following drive mappings:
Drive letter Is accessed from the ICA session as:
Client Drives:
A A
B B
C C
D D
Server Drives (after reassignment):
M M
N N
O O
You can do this during MetaFrame Setup or after MetaFrame has been installed.
See "Reassigning Server Drives" in Chapter 4 for instructions on changing the
server drive assignments after installation.
If you intend to remap the server drive letters, install MetaFrame and
remap the server drive letters before installing any applications.
If you remap the server drive letters, the following registry keys are searched and
all drive references changed to reflect the new drive letters:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\*
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\*
HKEY_LOCAL_MACHINE\SOFTWARE\Equinox\eqn\CurrentVersion
\NetRules