You can easily install a new LAN or network card without removing the existing. The existing card is built into the motherboard. See the link below for an example, that particular model is very reliable and not expensive.

As you have been inside you computer before you are familiar with the contents. On the motherboard you will see various slots, those nearest the bottom are likely the PCI slots. You will need to remove the metal piece on the rear of the case corresponding to the location of the slot you use. Insert the new card, press firmly down to seat then use the screw on the computer backplate to secure. Connect the CAT5 cable to the new card. Start the computer and use the CD that came with the new card to install the software. Done.

Here is a link that might be useful: Ethernet or Network card

Try this:

After the computer is started and you cannot connect to internet:

Go to the back of the computer, unplug the cable there, wait a few seconds, plug the cable in again.

I need to do that with my system sometimes.

dcarch

another thing to give a try is powering down your modem and router. I would do a full power down power off your pc's then unplug your modem and router from power, let set 5 mins or so then power up in this sequence your modem first let it get fully lit up then the router and let it get fully lit up then your computers. I have found that at times some of mine will drop the connection and have a problem gaining it back till I do that and re-establish everything fresh.

I appreciate all your comments. Thanks very much.

Dcarch and Ravencajun: I have done those things many times, and at times in the past they worked, but for this problem they are not working.

Owbist: Looks like your suggestion is my only hope. I will have another look inside my computer tomorrow or Friday, when I get some time. Are all such LAN cards the same? And what is a CAT5 cable, please? Can I expect that there is already one inside my computer somewhere? I didn't notice any cable running from the little metal box with the Ethernet and USB ports.

You have a CAT5 cable. It is the one that connects your router to your computer - the ethernet cable that plugs into the ethernet port.

Yes you currently have a LAN card installed but it is built into the motherboard and cannot be removed. Simply remove the cable Bob refers to from the existing socket on the rear of the case and insert it in the new LAN card. Then install the software and you'll be off and running.

All LAN cards are basically the same, the need a PCI port - those whitish slots on your motherboard very likely.

BE SURE to have removed the power cable from the rear of the case because even when the computer is switched off there is still power going to the motherboard. You might see a small LED light on there indicating the power is present. Also, place you bare arm or wrist on the metal casing as you insert the new card to dissipate any static eletricity.

Technically CAT5 refers to particular type of cable that meets certain specifications and often, but not always, used for a networking technology called Ethernet. The two terms are frequently interchanged. But that's neither here nor there.

If you've tried a new, known good, cable to connect from your computer to the router then the problem unlikely to be the cable. Although, for future reference, it's good practice to avoid sharp bends in any cable and you might want to slightly reposition your computer case to avoid sharp bends in your cables.

Before buying a new network card, I would suggest going into Device Manger and checking to see if there are any problems in your networking section. Even if nothing shows up, I would delete any entries and reboot the computer. That will cause Windows to reinstall the drivers.

If that doesn't work, you'll need, as others have suggested, a new network card. Almost any computer, electronics, or office supply store will have a limited and frequently expensive selection. You can save money if you order online. I've used a variety of network cards over the years although my preference is for Intel cards. They work flawlessly and are generally universally recognized by operating systems eliminating the need to install any drivers.

Thank you all. All this information is very helpful. I'm off to an early-morning medical test, but after that I'll have the rest of the day to work on this problem. I'll try that Device Manager thing first, Mike, and then order online if I have to get a network card. Fortunately, I can get Internet time on my husband's computer until it comes.

Hi, all you nice people who tried to help me. I decided since nothing else worked, I'd have to install a new network card, as suggested. A younger friend came over and did it for us, out of the kindness of his heart, but still no results. He took the computer away and had another friend work on it, and at HIS house, it did connect to the Internet. Long story short, the trouble turned out to be that the router would no longer work with my computer, and when a new one was installed, the problem was fixed. Since these friends were very, very busy for several weeks, I had to rely on my husband's computer for the Internet until the two friends had time to spare for mine, and I certainly do not begrudge the wait. Now everything is running fine.
I'm sorry for not reporting on this and thanking you all immediately, but certain other situations had arisen that kept me so busy that I forgot a few things I meant to have done sooner.

My only guess about the router trouble (I tested and found all the ports on it were still working just fine for my husband's computer.) is to wonder whether it could have been caused by my unplugging the ethernet cable from my computer a number of times when we were going to be away and there was a possibility of thunderstorms. I recall a box popping up requiring me to make choices about a network, which I didn't understand, because we have no network that I know of. We only plug into the same router and our computers are not connected in any other way. But I mention this in case it makes sense to someone here who knows computers, so that you can help someone else if they have a similar problem.

Again, many thanks.