Reset Default Windows XP Registry Settings

There is no way to reset all default registry settings in Windows XP.

If you would like to reset the permission of the whole registry, the following command tool maybe helpful:

SubInAcl

1. Download and install subinacl from:
http://www.microsoft.com/downloads/en/confirmation.aspx?FamilyID=E8BA3E56-D8FE-4A91-93CF-ED6985E3927B&displaylang=en


2. Create a file named reset.cmd in C:\Program Files\Windows Resource Kits\Tools folder.

3. Edit the reset.cmd file with the following content.

subinacl /subkeyreg HKEY_LOCAL_MACHINE /grant=administrators=f
subinacl /subkeyreg HKEY_CURRENT_USER /grant=administrators=f
subinacl /subkeyreg HKEY_CLASSES_ROOT /grant=administrators=f
subinacl /subdirectories %SystemDrive% /grant=administrators=f

subinacl /subkeyreg HKEY_LOCAL_MACHINE /grant=system=f
subinacl /subkeyreg HKEY_CURRENT_USER /grant=system=f
subinacl /subkeyreg HKEY_CLASSES_ROOT /grant=system=f
subinacl /subdirectories %SystemDrive% /grant=system=f

4. Enter into CMD prompt.

5. Enter the following commands one at a time and click Enter.

cd\
cd "C:\Program Files\Windows Resource Kits\Tools"
reset.cmd

6. After a few minutes by processing subinacl, the permission will be reset.


SOURCE: Google Group