CheckedValue in registry

CheckedValue is to control the button, rather check-box or radio button value, checked or not
and even selectable or not
by changing its DWORD value to 2 (out of 0 and 1)
that object is not selectable at all
I wonder if it is a bug of Microsoft or it is related to some policy settings, this trick is always mis-used by some malware and virus

the common example, in these key
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\NOHIDDEN
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
when CheckedValue changed to 2, users are not able to change 'hidden files and folders' inside "folder options"

strange enough....