Kindly I ask your attention.
Well, looks like you have to Google a bit to see what you are writing and asking.
Start Google and type:
What does sfc /SCANNOW do?
https/www.google.nl/#q=What+does+sfc+%2FSCANNOW++do%3F
sfc /SCANNOW, it checkes the System Files of Windows for errors and has nothing to do with the Registry of programs that can give some issues.
What do Registry programs do?
https/www.google.nl/#q=What+do+Registry+programs+do%3F
Well, programs have being registered at Windows Registry. Thoose programs put in the Registry more Registry Entries. Some work in combination good and some don't, all will be deleted when the programs has being deleted and some deinstallations leave some Registries behind that polute the system/give errors.
That's where a Registry program comes in for use, it will try to find thoose Registries and delete's or changes them. The so called Repair.
Well, there is another check like 'chkdsk', this will check the disk for disk error's and System Files too.
Google for:
What does chkdsk do?
And for chkdsk and sfc /scannow, check the net for How to Use. Copy the text lines into Notepad so you don't need to check everytime How to Use it on the net.
When you want to do the Windows Registry manually, make surten you look on the net for it. You might be able to type the registry key into Google and Google might find a link that can tell you If you can Or not delete it and what might happen. Use a phrase like:
HOT_MACHINE_KEY/Windows/Progams/Google/BlaBlaBlaWhatever deletion
Or,
BlaBlaBlaWhatever register key deletion
And so on.
Hopefully I let you known enough, that you will find the answers you seek!
Good luck and have fun doing it!
Best Regards,
MeneerWitte