Ways you can tell it's broken is:
Computer will not pull a DHCP address
Running the command "ipconfig" will result in an error message
Obviously, you wouldn't be able to ping any address

Most people, when it comes to fixing the TCP/IP stack in Windows, would run the command:
netsh int ip reset resetlog.txt

Then restart the machine.

This above command rewrites two registry keys that are used by TCP/IP:
SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\
SYSTEM\CurrentControlSet\Services\DHCP\Parameters\

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