Question : Cant connect to Internet --TCP/IP setting problems? XP Home

I am working on a XP Home machine(AMD XP 2000--224mb ram) that apparently used to be able to connect to the internet, via wireless (the story I am getting from the user) it stopped being able to connectt, so he switched to the built-in NIC.  That worked for awhile and now he called saying it wont connect and the screen goes mysteriously blank at times. I know int he past he has had some virus problems and spyware issues and I am not sure if this might be the case. Seeings I cant connect to the internet, I ran a virus scan (TDS3) and spyware scanner (adaware) off of an XP bootdisk to no avail, albeit the defintions are about a month old, but they found nothing.  When I boot the machine and go to network connections there are two cards - the wireless is the first network connection ( i disabled it as it wasnt working)  and "Local Area connection 2" is the built-in nic. UNder the status of "local area connection 2" it says 'connected' at 100mbps, but it is not sending or receiving packets. Activity says : 0 sent  - 0 received. when i go to command line and type ipconfig it says

connection specific dns suffix:
ip address.....:0.0.0.0
subnet mask.....0.0.0.0
default gateway......:

whne you try ipconfig /release it says it has been released
when you type ipconfig /renew it says "windows ip configuration error"
"an error occurred while renewing interface Local Area Network 2: the system cannot find the file specified"

 I have all the settings on the offending unit, the same as on the laptop in his office which can connect - IP and DNS are set to be obtained automatically. I tried right clicking in the network properties on "local area connection 2" and running the repair--no dice. I am really at a loss here. Could it be TCP/IP is messed up on this machine?  I can ping the loopback address and localhost, but nothing beyond that--isnt that indicative of tcp/ip stack being good?

Answer : Cant connect to Internet --TCP/IP setting problems? XP Home

Your ISP will usually only let ONE MAC address connect to its network.  If the cable/dsl modem is ISP owned, then this is why.
Putting things behind a router/switch means the single MAC address of the router/switch is in use.