I began my attempts to get personal with CLSHEAP several months back. Thanks for the point to NET RESOURCE!

>>What can be done to get a list of user/computer names logged to a particular domain?
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>Computer names can be done using the Win32 API quite easily; you can modify the sample code in my NETRESOURCE class to sniff out the machine names pretty easily. You can download the code from here on UT; you'll also need CLSHEAP. You have to read the code and have a clue about how the Win32 WNetOpenEnum and WNetEnumResource calls work, but that's pretty well documented in the MSDN library and in comments in-line in code.
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>Sniffing out users involves detailed interaction with the authentication provider(s) to find out what's legal - the ADSI or WMI interface would be the easiest solutions, and could accomplish the first task as well, so I'd invest my time in learning about ADSI's capabilities.