I tried doing this when I started using Vista RC2, using junction points,
but I never got it to work.  I ended up just moving the user shell folders
and pointing to the new locations with junction points in the original
locations.  Some of those folders (the larger ones) would be on different
drives for me anyway, and can even be network locations with Vista's
symbolic links.  The problem is that apart from the hidden AppData folder,
the user folder also contains the user hive of the registry (HKCU).

Anyway, this guy seems to have done it, but I really do not think it is
worth the hassle of moving the whole user folder, unless you have many
users.  And if you do, you might as well be using active directory and
roaming user profiles.  I think it is worth moving the TV recording from the
Public folder on the boot drive to another one though, to save wear on my
Raptor drives, and make things neater.

http://joshmouch.wordpress.com/2007/04/07/change-user-profile-folder-location-in
-vista/

ss.

????

Assuming you already have the drive, cant you just use the location tab in
the user files properties??