To most easily move all user files and user program files off your boot drive (an SSD in my case), follow these instructions.

FIRST, Create a restore point:
1. Open System by clicking the Start button, right-clicking Computer, and then clicking Properties.
2. In the left pane, click System protection. If you’re prompted for an administrator password or confirmation, type the password or provide confirmation.
3. Click the System Protection tab, and then click Create.
4. In the System Protection dialog box, type a description, and then click Create.

THEN: Go to System Recovery/Command Prompt:
Boot with the Win7 Install DVD, choose language, currency and keyboard, and hit Next.
At the screen with the “Install Now” choose “Repair your computer”
You will be asked if you want to “Repair and Restart” by the System Recovery options, choose “No”.
Then Make sure that Windows 7 is listed as one of the installed OS’s available for recovery, and that it’s selected and then press next.
You will be given a list of recovery tools.
Choose “Command Prompt”.

Find your virtual Windows drive loaded from the Win7 media (probably either C or X), find your actual Windows/SSD drive (D or E) and find your HDD (regular hard drive) (D or E).

In my system normally, C=SSD with Windows on it, D=HDD data drive

Using Win7 Update media, the drives in Recovery mode were set up differently, thusly:
X: virtual/temp Windows drive,
E: actual Windows/SSD drive,
D: HDD, hard drive I wanted to put \Users on.

Some report that System Recovery mode will set up their drives like this:
C: virtual/temp Windows drive
D: Actual Windows/SSD drive
E: HDD, they want to put /Users on.

In the command prompt you will be using Robocopy (NOT xcopy!) to copy c:\Users to d:\Users, then delete the old c:\Users, then make a symlink from c:\Users to D:\Users. Note that you must do these things in order, and you must not have a d:\Users dir before you do this.

NOTE: in the system recovery command prompt window, your drives are not the same as they will be after you leave recovery mode! So adjust the commands below for how the drives are in Recovery Mode, and then they’ll turn out correct later.

I used:
robocopy /mir /xj E:\Users D:\Users

To move /Users from Windows/SSD to HDD.
/mir tells robocopy to mirror the directories, this will copy all files and permissions.
/xj is very important, this tells robocopy not to follow junction points. If you forget this, you will have a lot of trouble.
Make sure no files failed to copy (FAILED column = 0).

Then you must remove the old Users Folder from the Windows/SSD (c:) drive, before you can create the symlink:
I used:
rmdir /S /Q E:\Users

Create a NTFS Junction/symlink that points to the new Users folder:

I used:
mklink /J E:\Users D:\Users

Use the /J switch to create a junction that’s a hard symlink. (If you use the /D switch, you’ll also have to edit the registry, cuz it won’t be a hard link.) Using /J, when Windows looks for the C:\Users dir, it will find it! But it will be on the HDD instead of the SSD. Tricky!

To see the proof of what you’ve created, still in the command prompt window, go into the actual Windows/SSD and do the “dir” command, and you’ll see:
” Users D:\Users”

Now restart and you’ll see /Users on your HDD, and there you go. No further configuration or fiddling required. New user profiles will all be stored on the d: drive, as will any user specific data. And it is achievable without any messing about in the registry, searching and replacing values, or having to mess with new profiles in any way. Totally set and forget.

Microsoft has graciously decided to get rid of the Documents and Settings folder in favor of the new Users folder in Windows Vista. This is nice because not only is it faster to type but its a little more familiar for Unix/Linux users. The one thing I still would love to see in the Windows installer, however, is the ability to choose the location of this Users directory (and heck even rename it). Unfortunately MS does not provide us that ability by default. To get that ability you have to modify the actual Windows installer.

So what if you don't want to have to re-install the operating system? Maybe you just want to move your data to the place of your choosing without any serious modification to your system. There are a couple solutions out there people have already written about.
They are:

1. Change the location of each data folder (i..e Documents, Pictures, Music) individually using Windows explorer settings.
   
2. Modify the Windows registry to reflect the new folder location
   
   

There are a couple of problems with these two solutions. The first solution means that you can only change specific folders such as Documents, Pictures, Music, etc. It doesn't solve the problem of moving hidden application data or other folders to the new location. It also becomes tedious to do so. Finally, if you want to move all of your user profiles to a new location each user must move the data their self. All in all its not really a solution to the problem.

While the second solution will work it is very dangerous to edit the Windows registry. Making even minor changes to the registry can render your entire system useless. I actually tried this method on Windows XP and was unable to get it working. The problem with editing the registry is that there are hundreds if not thousands of references to the profile folders within it and you may not find every one. Missing even one will prevent Windows or your software from working properly or even at all.

Thankfully I found an easier way.

This method requires that you use the Windows installation disc or use a WinPE 2.0 boot disc. To learn how to create a WinPE 2.0 disc go to http://www.msfn.org/board/lofiversion/index.php/t83722.html. Regardless of your choice you will need to get to the command prompt. If you are using the WinPE disc you should be immediately given a command prompt once it has finished booting. If you are using the Windows installation disc you can find instructions how on how to get to the command prompt at http://www.bleepingcomputer.com/tutorials/tutorial147.html.

WARNING: The following can be dangerous to your system. As with any hack you should always fully back up your entire hard drive just in case anything goes horribly wrong. If something bad happens to your system don't blame me... I warned you

For this example I am assuming that you want to relocate your Users directory to your D:\ drive. If you want to place it elsewhere, just change the commands accordingly. Now that you are at the command prompt, type the following commands followed by enter for each:

1. xcopy /E /H /O /X /Y /I C:\Users D:\Users
   
2. rmdir /S /Q C:\Users
   
3. rmdir "C:\Documents and Settings"
   
4. mklink /J C:\Users D:\Users
   
5. mklink /J "C:\Documents and Settings" D:\Users
   
   

What you've done here is copied everything in the Users directory to the new location and then created an NTFS junction to the new location. You might also notice that Documents and Settings showed up again. You thought Vista got rid of it for good didn't you? Many applications are hard coded to use the Documents and Settings directory and do not know that Vista has changed this. To make sure these applications still work under Vista Microsoft cleverly created their own junction from the older Documents and Settings to their new Users. You might ask why is it necessary to do change the existing junction then. Well as I discovered myself NTFS for some reason has a bit of trouble with accessing a junction of a junction. So when I first attempted this hack I encountered problems.

You may now restart your computer and you should have successfully moved your entire Users directory to your new location. Congratulations!

Update: After some further testing i've discovered something interesting. When using xcopy to move the data files to a new location the special folder icons for Documents, Pictures, Searches, Music, etc. appear to be lost. Also, performance when booting up again may seem slightly slower at first. So instead of using xcopy I tried using a backup program like TruImage to backup the Users directory and then restore it in the location I desired. Using this kept all the special folder icons and the system appeared to be a bit more snappy at first bootup. So while the method described works just fine, for performance and aesthetic reasons I would say backup/restore your Users folder instead. Thus the steps would be as such:

1. Backup C:\Users using a backup program
   
2. Restore the C:\Users to your new desired location (example: D:\Users)
   
3. Start WinPE or Windows Installation disc command prompt
   
4. Using the command prompt
   
   1. rmdir /S /Q C:\Users
      
   2. rmdir "C:\Documents and Settings"
      
   3. mklink /J C:\Users D:\Users
      
   4. mklink /J "C:\Documents and Settings" D:\Users
      
5. Restart