A Little More Specific: I connect through a D-Link DI-524 Router (it's a wireless router, but all of the computers are wired through to it), and all of my other computers work just fine. Up until the new computer replaced my old one, it had worked just fine. When I first installed Windows, I couldn't connect to the internet through the motherboard (Asus M2R32-MVP) input (Limited / No Connectivity, couldn't acquire a network address), so I brought in a really old 3Com router from an old computer and it worked. Barely. I just couldn't top speeds of 3kb/s, and about two hours later, it wouldn't load up anything. It appeared to be completely connected, but just wouldn't load anything. The same was still happening to the MB with the L/NC problem. I installed all possible updated drivers for everything (NIC, all MB drivers, etc), updated BIOS, etc etc, and nothing worked. So I went out and bought a brand new Linksys EG1032 NIC, and instantly had the same problems, where it wouldn't acquire a network address and had L/NC.
Troubleshooting I've Tried This is not all of what I have tried, but it's the most common solutions that I've done, haha. Through setting alternate configurations ins TCP/IP configs, I've managed to connect and have even had the status listed as "Connected", but still was not able to use any bandwidth. I've released / renewed my IP address, but cannot connect to DHCP. I've released and and renewed the router through this computer, to no avail. I'm not terribly experienced with computers (especially software, *especially* networking, haha), but I'm experienced enough that I've built and maintained my last three computers for myself and the last 4 for members of my family, so I like to think I'm at least marginally inclined, haha. I don't know how many times I've reinstalled Windows, updated drivers, reboot, rinse, repeat, reset routers, reset the modem, reboot, rinse, repeat copy/paste into Notepad and run up two flights of stairs and execute to no avail and run back down two more and net ranger my way to the next solution that doesn't quite fix my problem. It's getting frustrating! =D
So at last, having seen the majority of possible fixes come from this website, I decided to register and see if anyone would be willing to try and help me out. It seems like it would be *such* a simple solution, because the problem appears so straightforward... it might just be that I'm overcomplicating it and can't see the answer sitting right in front of me.
Also worth noting: Although I can't 100% confirm its' functioning, I don't believe the problem to be a faulty cable. Not only did it worked perfectly up until the new computer, but it even partially worked on the new comp with that old 3Com NIC, while simulataneously having the problem with the MB ethernet adapter. I mention this because the cable is a bit difficult to maneuver, seeing that it is running through two stories of the house via an air duct. =)
Any help is amazingly appreciated!