I have to agree with sari and 1101doc's comments .
Having been a Beta tester for Registry Cleaners as a hobby , Rule 1.
If you have to ask , "Which registry software is best?" your probably jumping in way too early Juanita . There will be the ocassional time when you'll need to access your registry for minor changes , which should be done in REGEDIT .
When that time comes be guided by an expert , when in doubt do nothing
Read a "trusted source" about the Registry and begin to understand and learn what it is .Rule 2.
ERUNT : make a .reg backup before making any changes to your system . Before installing new software , if something doesn't workout you can revert back to a pre-install state .
The Registry really does not need regular cleaning unless your making large changes to your system on a daily or weekly basis . I did notice when running Win 98 SE that registry cleaning had a positive effect on performace , not so with Win XP , in my opinion .
ERUNT does have a Registry defragmenter of sorts called NTREGOPT.EXE which can be found in your C:\Program Files\ERUNT directory .
Erunt can't replace Windows System Restore , or a image Backup of your Hard Drive .
Play safe and ask if you are unsure