|What kind of computer is it DerbyDad? Is it custom built or a brand name and if brand name, what's the make/model. If it's a Dell, it may very well be a NIC issue. We have had Dell rammed down our throats at work (you guessed it, I don't care for dell) and the one model has consistently been having major NIC issues.|
In this case, you've already isolated it to the one PC so you know it's either hardware or software. Normally in a case like this I would first run antispyware and antivirus to ensure it wasn't a spyware bloat issue.
If that didn't fix it, I would then go into Device Manager and uninstall the NIC and then reboot and let XP "find" it again.
If that doesn't work, I would then un/reinstall the TCP/IP stack and see if that doesn't do the trick. If it doesn't, the next thing to test would be the NIC.
If you try a new NIC with no improvement it may be time to backup that unit and wipe it and do a clean install of your OS.
Just as an aside, with the Dell's at work that have bad NIC's, when you try my first step (unistalling the device) when reboot is done, your NIC would now show up as "Local Area Connection 2" and if you did it again, you would then see "Local Area Connection 3" and so on and so on and none of them would work and the only fix we found was to reinstall from scratch. But of course, since the NIC is borked, it's only a matter of a few days and it starts puking again and you have to replace the mobo.