All user’s registry settings (HKEY_CURRENT_USER) are stored in the registry hive file NTUSER.DAT in the user’s profile directory. When solving errors, this file is often deleted. This might do the trick, but is rather drastic as all registry settings are lost.
Deletion of a single registry key is far more likable. You can do this by loading the hive in the registry editor in a temporary key in HKEY_LOCAL_MACHINE.
Load the hive (GUI)
1. Start regedit.exe.
2. Select HKEY_LOCAL_MACHINE.
3. select File -> Load Hive from the dropdown menu.
4. Select the NTUSER.DAT file from the user’s profile directory.
5. Enter the registry key’s name: Temp.
6. The key HKEY_LOCAL_MACHINE\Temp will appear. You now can change, add or delete any key and value you like.
8. On logon the registry hive is copied from the profile directory to the computer’s local hard disk and the other way around on logoff. This means it’s useless to change the file NTUSER.DAT when the user is logged on to any PC in the network.
Because the file will be locked on loading the hive, you must remember to unload the hive before user’s logon. To do so, select the key HKEY_LOCAL_MACHINE\Temp and use the Unload Hive option in the file dropdown menu.
Load hive using the command line
Loading the hive (step 2-5) can be replaced by the command:
Reg load HKLM\Temp [filepath]
Unloading the hive (step 8) can be done by:
Reg unload HKLM\Temp
Example: Delete HKLM\Temp\Software\Adobe\Acrobat Reader if the user is experiencing Acrobat Reader problems.
Source: http://www.zeda.nl/index.php/en/load-user-registry-hive-in-regedit