Hi,
I can easily turn off System Protection via:

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SystemRestore]
"RPSessionInterval"=dword:00000000

However, I also need to set its Disk Space Usage property to minimum (1%).
System Properties > Configure > Disk Space Usage
I couldn't find the key for Disk Space Usage, please help.
I need to do it only via registry.
Thanks.

Hi omidimo

 Follow these steps 

1) Go to control panel and select System and security.
2) on that window you can find a System Protection, click on it.
3)You will get a system properties window.
4)you select the System Protection TAB and click on configure , it will open a new tab.
5 )On that new tab you stop the "Turn off System Protection".