LAN HELP!

I own an Inspiron 8600 that is nearly 2 1/2 years old. I recently got RoadRunner DSL but whenever it is plugged into the computer via ethernet cable the computer responds, "Limited or no connectivity." I called the cable company for support and they walked me through a few fruitless exercises before advising me that their modem wasn't working and I had to get a new one. I did so, and the situation is exactly the same as before. I perused some other postings on this forum yesterday and tried some things at home but with no success.

My IP configuration read as follows:
WINDOWS IP CONFIGURATION:
Host Name: PHOYLE Primary
DNS Suffix: _________
Node Type: Mixed IP Routing Enabled: No
WINS Proxy Enabled: No
DNS Suffix Search List: nyc.rr.com

ETHERNET ADAPTER LOCAL AREA CONNECTION:
Connection-specific DNS Suffix: _________
Description: Broadcom 440x 10/100 Integrated Controller
Physical Address: 00-0F-1F-1E-5E-F5
DHCP Enabled: Yes
Autoconfiguration Enabled: Yes
Autoconfiguration IP Address: 0.0.0.0
Subnet Mask: 0.0.0.0
Default Gateway: ________
DHCP Server: 255.255.255.255

I also tried to release/renew the IP Configuration at the command prompt and it gave me the following response:
"Windows IP Configuration An error occurred while renewing interface Local Area Connection: unable to contact your DHCP Server. Request has timed out." Anybody have any idea what to make of all this?