How to configure a network card to use DHCP server via registry in Win98 WinME

Do you mean in code, or manually?

You can manually set this in XP (assuming Me/98 is similar)
Control Panel->Newwork Connections->Local Area Connection->Properties (button)->Internet Protocol TCP/IP (properties button)->Obtain an IP address automatically (option button).

Hope it helps!

This may be helpful:

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"WMI Tasks for Scripts and Applications"

Search for enableDHCP (the example is halfway down the page)

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wmisdk/wmi/wmi_tasks_for_scripts_and_applications.asp

strComputer = "."
Set objWMIService = GetObject("winmgmts:\\" & strComputer & "\root\cimv2")
Set colNetAdapters = objWMIService.ExecQuery _
    ("Select * from Win32_NetworkAdapterConfiguration where IPEnabled=TRUE")
 
For Each objNetAdapter In colNetAdapters
    errEnable = objNetAdapter.EnableDHCP()
Next
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Hello?

I've already found a way...

Check the network adapter first located at
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Net\ 000x
where x would be the adapter number to be modified in
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Nettrans

set IPAddress and IPMask keys to 0.0.0.0,delete any default gateway key and reboot.
then ip renew and release and it works.