Change the drive for My documents folder

I haven't tried this, but perhaps you could try adding a system environment variable? Right-click "My Computer" click "Properties," click the advanced tab, and click "Environment Variables." The upper box is user-specific, the lower is system-specific.
For the path use the %username% variable to assign it to the currently logged in user. (eg. D:\mydocs\%username%)

FOR ALL NEW USERS
1. Create a temporary user to make a new template or use an existing user as a template user.

2. Change the following registery keys.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders]
"My Pictures"
"Personal"

Use something like: E:\USERS\%username%

3. Log off. Then copy the NTUSER.DAT file from that user to the Default User Profile path replacing the older file.

FOR EXSISTING USERS
Create a onetime login script or a simple batch file that can modify the registry key above. Users should be prompted to log off and then log back on for the changes to become effective.

FOR ALL EXSISTING USERS - AUTOMATED
This one would require you to change the registry key for each user that has an account and has logged onto the system in the past. It is also possible to do this via the NTUSER.DAT; however, if each user's settings are different, this can cause major problems.

There may be other ways to do this that require various levels of programming or scripting. If you are talking new users, then #1 is good. If you are talking <100 users, #2 should be adequate--in fact, there is not reason that #2 couldn't work for any number of users. It just requires them tolog on, run script, then log off & back on again. Of course, you can automate the running of the script and logging them off.