A lot of you probably know this already, but I wanted to list these steps for the record.  If you are debugging an application issue or just want to make a quick change to your image and redeploy it without needing to open Target Designer and rebuilding your image, you can do the following:

1. Run regedit.exe on your development machine
2. Click on HKEY_LOCAL_MACHINE in the registry tree, go to the File menu and choose Load Hive...
3. Browse to \Windows\System32\Config\ in the location where you built your XP Embedded image
4. Load one of the hives named *.SAV - this is because the FBA process copies the hives with *.SAV extensions over the same hives without the *.SAV extensions before performing any other actions, so if you want registry changes to take effect during FBA you have to change the *.SAV hive
5. When prompted for a hive name, enter a name that does not clash with an existing registry hive on your development machine
6. Make any desired changes to the registry in the Regedit UI
7. Click on the hive name that you provided in step 6 above, go to the File menu and choose Unload Hive...

After following these steps, you can deploy your image and any registry changes you made will take effect in your embedded OS.  Hope this helps.....