Windows 7: Network Cable is unplugged

This is a desktop and is connected to the router by wire not wirelessly. I bought a router yesterday and I followed every step in the manual exactly. After repeating it a couple times, I still can't get any internet. Before that, I had internet and everything was working fine. Then I went to my Network and Sharing Center and I pressed something either the one with the computer name and the line connecting to the internet globe or in view your active networks section. When I pressed that, all of a sudden there was an "X" on the line connecting to the globe. I called Comcast to see if they can help me and the lady told me she cannot find my network adapter.So I went to my other desktop which is also connected to the internet by wire and she found that computer's network adapter. I checked everything, checking if the ethernet cord is all the way in and make sure its connected, still it says network cable is unplugged even though the ethernet cable is plugged in all the way. I reinstalled my network adapter and still it cannot connect to the internet. Please tell me what I'm doing wrong and any way to fix it? Thank You
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I would try another ethernet cable. Maybe yours is broken.

Has the network socket accidentally been disabled in windows or BIOS perhaps?

Try connecting directly to the Broadband Modem, bypassing the Router. Does that work as it did before?

If not, try doing a System Restore to before you started installing the Router. Make sure it works without the Router, then start installing the Router again.

@whs i tried that and its still the same
@Banoz how do I know if the network socket has been disabled?
@Ztrucker how do I do a System Restore?

Firstly try this,

1. Power down the computer
2. Start the computer in BIOS
3. Reset BIOS to defaults
4. Power down the computer
5. Unplug the power cable
6. Press and hold the power button (with the cable disconnected) for about 10 seconds
7. Replug the power cable
8. Power on the computer

then;

Start > right-click on 'Computer' > Manage > Device Manager > open network adapters, right click and open properties on your adapter > advanced tab > look for 'Link Speed & Duplex' and change value to '100Mbps Full Duplex'

@SolarWing
Thank you, thank you, thank you so much!!!!!!!!! I have internet now. I did not reset my bios because I was too lazy to fix it back. I would definitely pay you if I could so again thank you so much for helping!!!!!!

Pleasure, glad it worked for you.