Please, I need a Win32 class (like Win32_SystemEnclosure) with which I can get the serial number of a computer's Motherboard

Like the US court says to Sony, "that's your software, but not your computer". And since a user who buy a computer is free to change every part of it, binding a licence software to a piece of hardware not related to the software itself is somehow unfair: volume number can be changed, network adapter can be changed, even a mother board can be changed. And there is no reason someone have to ask for your permission.

Not to mention that a user -according to the laws of the most of, for example, European countries- can make any number of copy he wants for his own personal use. (So whatever mechanism trying to avoid it, can be legally required to be disabled...)

You better not to sell the copies (you know that information propagates by copy and that copy bytes is the way computer internally work, so it cannot be an "exclusive operation", since you are a programmer so I don't need to tell you ...) but to sell "support" to the people who pay you.

Just like a plumber is payed for the time he spend operating a plant, not for the number of time a tap is opened and closed.

In case you want to be able to track who's using your software, implement a registration mechanism and provide each user an id and implement a client server mechanism to track how many "session" are sourced by that id, possibly using encrypted data.

This let the user free to change or move the software between computers but limits the number of contemporary execution he can do. This can be done with no particular restrictions, apart you inform the user that such a mechanism exist and who (person) is responsible for the management of the usage information you will collect (this is to comply with privacy regulation eventually in place)

Perhaps you'll find this little utility of some use:
CIMTool for Windows Management Instrumentation - Part 1[^]

You can use it to browse the information available through WMI, just select the class you want to query, and choose File->new->query.

I think I would collect more than one system parameter - as it's kind of nice to be able to get a new motherboard without having to go to all the trouble of getting a new license. A combination of harddisk serial number, mac address, harddisk serial number that would allow the user to upgrade a faulty part of hs system would perhaps be a good idea.

Best regards
Espen Harlinn

Agree with solution #1 - a better idea is to use the MAC address. This is not completely hack proof but at least it is always there and is meant to be unique. You can use WinApi GetAdaptersInfo function for example.

void GetMacAddress()
{
        CString m_MacAddressStr;
	IP_ADAPTER_INFO AdapterInfo[16];       // Allocate information for up to 16 NICs
	DWORD dwBufLen = sizeof(AdapterInfo);  // Save memory size of buffer
	DWORD dwStatus = GetAdaptersInfo(AdapterInfo, &dwBufLen);
	if (dwStatus != ERROR_SUCCESS)
	{
		return;
	}
    
	// if we get here, we have at least one adapter, and data in AdapterInfo is valid
	
	PIP_ADAPTER_INFO pAdapterInfo = AdapterInfo; // Contains pointer to current adapter info
	do 
	{
		m_MacAddressStr.Format("%02X-%02X-%02X-%02X-%02X-%02X", 
			(int)pAdapterInfo->Address[0], (int)pAdapterInfo->Address[1],
			(int)pAdapterInfo->Address[2], (int)pAdapterInfo->Address[3], 
			(int)pAdapterInfo->Address[4], (int)pAdapterInfo->Address[5]);
		
		pAdapterInfo = pAdapterInfo->Next;    // Progress through linked list
		
	} while (pAdapterInfo);
}

By the way, if you have a serial port on the computer on which you are running your code, the chances are you will get the PPP (point to point protocol) adapter first in this list of adapters. Which happens to be "44-45-53-54-00-00". So you should skip it and look for a real MAC address of the first network interface. Most modern PCs will have 2 or more (WiFi and Ethernet, etc).