The use of DWORD as a type should, in my opinion, already state that the value is always non-negative. Explicitly checking for it might even be a bad thing, as it can distract the reader. He might not check the type and let negative numbers pass in as arguments because he trusts that the >= 0 check handles them. (This of course might, or might not get caught by the <= WHATEVER check).
You seem to be arguing that, when viewing a conditional, the reader should have to verify the type of the variable in order to glean understanding of the logic. I don't like that. I don't want people to have to double-check variable types, and I want everyone from the project lead to the new college hire (who doesn't have an intrinsic understanding of DWORD implications) to, at a glance, understand that I'm checking for a range of values.
Of course, all of this would be handled by a native range expression, but we don't get that in C/C++. And, as I said in an earlier comment, project- or company-specific macros just add another layer of required comprehension.
