Search notes:

Registry: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion

This key stores information about the system such as Product Name (for example Windows 10 Pro), CurrentBuildNumber …

Some sub keys are

PathName and SystemRoot

At least on the computer I am currently working on, the values of PathName and SystemRoot are C:\Windows.

ProductId

The value of the product id.

See also

There is also a HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion