Larry,
Much later I found your technique had the same problem as getting the "MAC" from the Registry - if you change the network card, neither the Registry OR the GUID base info change <s>. I ended up using a .DLL that someone posted on Compuserve and it seems to work reliably on all the OS's even though the author suggested it might not work on some (Win95 specifically).

Rick

>>What fuction return the MAC Address?
>
>Check out this message for some code that might help.
>
>Message#477983 (http://www.levelextreme.com/wconnect/wc.dll?UniversalThread~?2,15,477983)
>
>HTH.