Keep in mind that link is to WinCE 2003 development resources.
For WM6(.1), take a look at
http://msdn.microsoft.com/en-us/library/aa912217.aspx for starters. That will tell you how to look at existing registry settings.
Keep in mind that each device manufacturer's version of the OS will differ slightly. So will its customizations. Hence, the set of registry settings, and even the meanings of some values, will differ between the manufacrurers.