I do a Google search and find people wanting to restore their registry to the original state. People have suggested to use Windows Backup and Restore but it fails big time because it does not delete newly added registry. It only restores registry entries that was modified. If only people knew about this software! It's one of its kind, I have not come across any other software that delete registry entries and restore the registry entirely to a previous time. So even if my registry becomes corrupted, the software would re-add what was lost.
Now every time I re-install my Windows XP, I will be sure to analyze my registry so I can restore it in the future.
If you just want to backup your registry, add Drive C to ignore list. I added Desktop and My Documents.