Registry Healer by default stores .reg backup files in folder "C:\ProgramData\RH_Backups" or "C:\Documents and Settings\All Users\Application Data\RH_Backups". You can quick open this folder from the Start menu -> Programs -> Registry Healer -> Open Last Used Backup Folder.
In backup folder you can find all created .reg backup files. They have filenames of "id_yyyy_mm_dd.reg" format, where id is an identifier ("paths" for invalid paths, "empty" for deleted empty entries, etc.), yyyy - year, mm - month, dd - day of creation date.
Double-clicking on a backup file in explorer will restore all information from that file (after you answer "Yes" on the confirmation dialog).
If you found a problem with your computer after using Registry Healer you may restore the most recent backup file, then check for the problem. If the problem persists you may restore next backup and check for the problem again. Thus you can figure out what backup contains a problem registry key that should be added into exclusion list.
Note that backup files should be restored in backward order of creation (last created - first restored).