Originally Posted by Mike-Techno-Thug
A few things before picking up a new ethernet card:
1.Test your current ethernet cable
Newegg.com - Rosewill RTK-T05 Network Cable Tester
Or have someone test it out for you in a shop or retail electronic store.
2.If you say the router is not the problem, call your isp company and have them run a test from their head quarters.
If they find any drops of data packets from them to your cable modem, they should replace it easily.
3.If both of them are not at fault I recommend you pick up a new ethernet card.
Best buy should have some on sale right about now, since the school year is kicking back in.
He said he already tried replacing the cable. And he tried all of the ports on his router, and he also still has connection via wifi from his phone.
One thing to try, if you have another computer, plug it into the ethernet cable and see if the connection drops.
Do you have a router / modem separate, or are is it a single box (modem) with several ports on the back / wifi built in?
If you have 2 separate boxes (router / modem), then unplug the router, and plug directly into the modem. If connection keeps dropping, then call your ISP to get the modem replaced. If the connection doesn't drop, then I would look into either looking to see if your router has a firmware update (can be found on the manufacturer's website usually), or replacing it all together.
However, if the secondary computer doesn't drop connection at all when connected to either, then I would say it'd be an issue on the built-in NIC in your computer. Get a new ethernet card (yes you would just plug it into an open PCI slot) and see if that remedies the issue. New cards are usually ~$20.