How can I modify windbg is using ring0 on single pc?

well it is still stactic all you can do with local kernel debugging is watch
read and write to user and kernel memory that is all
no dynamic commands like t,p,g , no break points bp etc are avl
in xp too that means it is of practically not much usefull

well if that is what you would like to then livekd does that for you in w2k too
and even older versions of windbg is sufficient