My friend's computer wouldn't access the internet, and so I agreed to take a look at it. (It's hard wired by ethernet cable.)
I went through a VERY painful, tedious process getting the device manager to populate (due to some setting it was empty), then in turn, to get the darned connections to show up, and the computer STILL won't connect to the internet.
The problem appears to be that it won't renew (or obtain in the first place...) an ip address.
I brought my laptop over (which has vista as opposed to XP) and hooked it up using the same port, line, etc.It had the same problem initially, but vista was able to sort it out, and after that I got on it just fine with my laptop.
But for some reason the XP desktop isn't working! Waaah! Any ideas?
Sounds like the IP may need flushed from the system, its a common problem.
Have you tried clearing the problem using the repair option?
Where does the network cable connect to? If he has a router power it off for 5 minutes or more and disconnect the cable, also shut down the PC. Before powering on the router connect the network cable to the PC, power on the router and then the PC. Test the connection when desktop loads.
If still failing open up the command prompt (DOS) and type ipconfig this should populate with IP Address, Subnet Mask, Default gateway. If any of these are missing the settings need renewed, flushing the IP will force it to renew.
Run a search on Google for flushing IP address on Windows XP if none of the above work.
To renew your IP address type the following at a DOS prompt: ipconfig /renew.
First try Gavin's suggestions, but I would even go further and turn off your broadband modem as well (provided that they have broadband). XP is usually good at picking up IP addresses as I have been able to switch between routers on the same computer without issue.
If all else fails, you can try reinstalling the network components in XP to see if that fixes the problem.