Please try the code below. I assume you are a Domain Administrator.

code:
CLS
$nul = SETCONSOLE("MAXIMIZE")
Color r+/n
SMALL ; Display in small character mode for testing
at (2,8) "Hello, @userid"
?   ; add a blank line
IF INGROUP("Domain Admins") = 1
	? "You are a Domain Admin"
ELSE
	? "You are NOT a Domain Admin"
ENDIF

This code should work. If this code does not show saying "You are a Domain Admin" (when you are one)
then you must have some other issue related to Windows NT/2000 and not KiXtart.

Make sure you have the same version of KiXtart on PDC and all BDCs and if local, then every machine running v3.63 also.