If you are unable to use the Remove button in Control Panel \ Network, use Regedt32 to delete:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\<adapter>

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\NetworkCards\<#>
(If only one adapter is loaded, <#> will be 1)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\<adapter>

Shutdown and restart Windows NT.