By default, Windows Vista, like all previous versions, insists on saving user data on the same disk as the system files. This may be fine for many people but I really don't want it to work that way. Before Windows Vista, you could edit the registry to move the folders around. Now in Windows Vista, Microsoft has added support to move the folders directly from within the file explorer which, in theory, should simplify matters. However, it doesn't always work and many applications fail to save in the new location. What is even worse, it appears to be impossible to change the location of the public folders from the GUI – even though the text in the GUI states that it is possible.
Realising that doing the changes via the GUI was totally worthless I tried to find another way. What worked very well for me was to change the two keys ProfilesDirectory and Public under HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows NT \ CurrentVersion \ ProfileList.
The change to the key Public affects all users in the system whereas changing the key ProfilesDirectory only affects accounts that are created (or rather when the user first logs on) after the change was made. I recommend you create an Admin user at the end of the Windows Vista installation process, make the changes to the registry and then add normal accounts for the users who will use the system.
As always, be very careful when changing the registry as a mistake could potentially wreck your system.