Networking not available at startup…

I am running Windows XP Professional with all current updates, and all current drivers. When Windows starts up and loads the desktop, it takes anywhere from 1 to 5 minutes before the NIC seems to start. It’s like it isn’t even there. Even trying to open the Network Connections control panel does nothing but lock up the Start Menu. I have experienced this problem with a laptop computer also, using a modem. Desktop is home built, laptop is IBM iSeries.