renewing IP address at startup after removing router

:-)

I connected my Win2000 machine to my DSL (Telenet Belgium) modem through a
router (D-Link DI-604) yesterday, just to test the router. Now that I've
connected the computer directly to the DSL modem again, it fails to
automatically get a dynamically assigned IP address at startup, and I have
to do an "ipconfig /renew" each time. Apparently Windows still thinks the
router will take care of the IP address.
Can anyone tell me which setting I should change to make it clear to Windows
that the router is no longer there, and it should negotiate an IP address
itself?

All help/suggestions welcome!

Marc.