ERUNT and NTREGOPT are two extremely useful tools you can use for your registry.
Those are not registry cleaners *per se* and they wont fix errors, but ERUNT is one of the best programs to schedule automatic registry backups, it also allows manual backups on demand.
NTREGOPT is a tool which can "defragment" and shrink your registry.
I am using ERUNT myself for years – it also works on Vista and Win7, even under 64bit.
How it works: With Erunt your PC performs an automatic registry backup every day which it saves to your C: drive under C:\Windows\ERDNT. For each day it creates a folder with the date as file name. You have the option to specify the days to keep, by default it keeps the last 30 days.
You can also make a quick command/batch and name it "Backup Now", so it would immediately backup your complete registry on demand.
"C:\Program Files (x86)\ERUNT\ERUNT.EXE" "%SystemRoot%\ERDNT\#date# #time#"
I put this in my computer's start-menu, and every time i change something in my registry i can click on this and it saves the complete registry in a folder with Date/Time.
Now, here's why ERUNT is extremely nice:
In each of those backup folders it also puts an *.exe file which automatically restores the saved registry.
If you have a total PC crash with a corrupted registry, you can boot into safe mode or even from a DOS disk..and then you go into the folder where the backup is.
You simply execute the *.exe and your complete registry is restored!
Feel free to read more about registry backup here.
