>>>Hi,
>>>
>>>I use some code to generate a number based on a PC's hard disk serial number and the MAC address. Recently, I have one client out of a couple hundred that this number changes on sporadically. I wrote a program to display what the serial number and MAC address are and the MAC address has changed from a couple weeks ago. The client says the NIC has not been changed.
>>>
>>>I thought the MAC address was tied to the NIC. What could cause this to change?
>>
>>How are you fetching the MAC address?
>
>VFP code:
>

>DECLARE INTEGER GetAdaptersInfo IN iphlpapi ; 
>STRING @pAdapterInfo, LONG @pOutBufLen 
>
>LOCAL lcBuffer, lnBufsize 
>lnBufsize = 0 
>lcBuffer = "" 
>= GetAdaptersInfo(@lcBuffer, @lnBufsize) 
>lcBuffer = Repli(Chr(0), lnBufsize) 
>
>IF GetAdaptersInfo(@lcBuffer, @lnBufsize) <> 0 && ERROR_SUCCESS 
>* =MESSAGEBOX('MSI Card Not Found',64)
>ENDIF 
>
>LOCAL lnAddrlen, lcAddress, ii
>lnAddrlen = Asc(SUBSTR(lcBuffer, 401, 1)) 
>lcAddress = SUBSTR(lcBuffer, 405, lnAddrlen) 
>lcThisID = ''
>lcThisHex = ''
>
>FOR ii = 1 TO lnAddrLen
>	lcThisID = lcThisID + ;
>			IIF(ii>1, ',' ,'') + ;
>			ALLTRIM(STR(ASC(SUBSTR(lcAddress,ii,1))))
>	
>	lcThisHex = lcThisHex + ;
>			IIF(ii>1,':','') + ;
>			RIGHT(TRANSFORM(ASC(SUBSTR(lcAddress,ii,1)),'@0'),2)
>ENDFOR
> 
>RETURN lcThisHex

According to the GetAdaptersInfo documentation:

In versions prior to Windows 10, the order in which adapters appear in the list returned by this function can be controlled from the Network Connections folder: select the Advanced Settings menu item from the Advanced menu. Starting with Windows 10, the order is unspecified.

Is the system returning the address for a different NIC?