Need to change a drive letter from outside the OS

Hi, so I've done a whoopsie. I had windows 7 on a SSD drive, assigned C: by windows 7, but it was full so I decided I'd clone it onto a bigger SSD drive using Acronis Disk Director. Went swimmingly I thought, both drives contained the same data. I wasn't too sure what my next step ought to be, whether acronis will have sorted it so that my new SSD now has the orginal SSD's drive letter or not. If it did, it will be mean a simple transition. But you guessed it, it left the drive letters the same, so when I booted up, it loaded from the orginal SSD. I then changed the original SSD drive letter, and used EasyBCD to remove the original boot and create a new one with the new SSD.
Unfortunate now when I boot up Windows 7 I get a Preparing Your Desktop message for a couple of mins, but it's then followed by a screen with a cursor but no desktop icons or taskbar. It also seemed unresponsive to keyboard strokes. Any ideas?

Boot into safe mode and press CNTRL-ALT-DEL. Select the task manager and select file and run.
Enter explorer.exe. When the explorer opens see what drive letter windows is using as the system disk.
Then select regedit and navigate to HKEY_Local_Machine\System\Mounteddevices.
Look for \DOS\Devices\?: where the ? is the drive letter that the system was using. Change it to C:
First look to see if there is another \DOS\Devices\C:, if there is, change that letter to an unused letter before
changing the system used drive letter to C:

Reboot and you should be all set.
You will also need to reset the system restore because it will have a drive C: that it can't find.

That's awesome!!! Thanks so much!
Many kudos to you, sir!

You are welcome.

Also thanks for the edit Brink. As always, your tutorials are great.