Paisano,
Starting with Win2k, to speedup boot times, I started using multiple disk installations: C:\Windows; D:\Documents and Settings; D:\Program Files; C:\pagefile.sys (very small and fixed in size to avoid hangs in booting and shutting down); D:\pagefile.sys; etc. It will work best if your T:\ drive is as fast as your C:\ drive otherwise and you may slow down your system.
The best way to arrive at such an install is with an unattended installation script. Now days there are handy utilities such as n-lite and v-lite that make this fairly easy to do. Again and for future reference, it is best to do this at installation with a properly modified unattended installation. Assuming that you do not wish to go that route at this time, here is how I would go about doing it:
Please understand that I pretty much avoided/skipped Vista and have not tried this in Win7 x86, my current OS, much less X64. I also know that the X64 registry is somewhat harder to work with in that it seems, to me anyway, that some parts of it are not easily modifiable. Therefore I recommend doing this:
Bootup using UBCD4Win (Bart'sPE). There may be other "Live CDs" that will work but Bart's is the one I use and know. First, open one of the file managers such as X2, there should be a shortcut on the task bar, and COPY ONLY (do not Move or Delete anything at this point) "C:\Users\" to where you want it to be when done, in your case "T:\Users\". Reboot normally to the hard drive.
Now install jv16 Powertools so that you can use the "Find and Replace" registry tool. There may be freeware utilities around that will also work but I do not know about them and I know that jv16 Powertools will work properly even when booted into a "PE" disk or "Live" environment. I believe a trial version will work just fine if you do not wish to purchase it. Use the "Find and Replace" tool to find all instances of "C:\Users\" and replace them with "X:\Users\" or in your case "T:\Users\". Also, look for and replace any and all other ways or instances where "\Users\" is used, for example "%SystemDrive%\Users\".
Now reboot into Bart's or UBCD4Win and open one of the file managers such as X2 and MOVE (or copy to and then delete) "C:\Users\" to "T:\Users\". At this point there should be no "C:\Users\" and "T:\Users\" should contain all needed files and folders.
Now go to Start/Programs/Registry Tools/Registry Editor PE and start it; be sure to select all the "ntuser.dat" files located in "T:\Users\" (should be one in each user's folder). Now start jv16 Powertools and redo all the "Find and Replace" runs/jobs that you did before and repeat them. THEN REPEAT THEM AGAIN (THREE TIMES TOTAL)!! If any instances of "C:\Users\" are found open REGEDIT and search for them and delete them. The reason they were not replaced is that there are already entries reading "T: \Users\. . ." and they cannot be replaced and so must be manually deleted. Now close all programs and wait for them to completely close and then reboot to hard drive and rerun all the "Find and Replace" runs/jobs in jv16 and again manually delete, if necessary, any instances of "C:\Users\" or "%SystemDrive%\Users\", etc.
Hopefully at this point you will not find "C:\Users\" on the C drive. If you do it is most likely because some installed program(s) has it written into it (them) that the user folder is located at "C:\Users\". If so it may be possible to track down the *.ini file and edit it (them). If "C:\Users\" continues to appear try uninstalling, completely, the program(s) and then reinstalling it (them) after a reboot. If "C:\Users\" still appears it will take a clean and modified unattended install of the OS.
Hope this helps.
