Any Drive Letter can be hidden from the Windows Explorer View. This is done by adjusting certain value settings in the Windows Registry. Values can be changed with the Registry Editor regedit.exe. Do it at your own risk and only if you have a slight idea of what you’re actually doing!

TweakUI uses…

Group Policy uses…

“Windows XP can hide drive letters. You hide them by setting NoDrives in
the key
HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer, but it’s
easier using the Tweak UI category Drives. The trick is figuring out the
value to put in the REG_BINARY value NoDrives. Each bit in NoDrives, right
to left, corresponds to the drive letters A through Z. To hide drive A, turn
on the first bit. To hide drive B, turn on the second bit. Turn on the bit
representing each drive that you want to hide. This math is easier if you
use Calculator in Scientific mode.”

Chapter 5 Mapping Tweak UI
Microsoft® Windows® XP Registry Guide