Dell Dimension 2400 with Broadcom 4401 Onboard NIC/Cisco Catalyst 2950 Switch

Ethernet card takes too long to negotiate with Cisco switch and fails to get DHCP Address. Resolution: Press Pause/Break on keyboard after BIOS until port is negotiated on switch (port is green), hit ESC, and DHCP will get address.

Another option might be to adjust your spanning tree protocol (STP) settings to allow portfast for all non-uplink ports (ports that connect to a leaf object, not another switch/router).