well lets see if I can take a shot at this..
I'm going to throw a few possible solutions at you instead of only one at a time, to speed this up.
Open a command prompt and type: ipconfig and press enter... What does it say your "default gateway" and "ip address" is? Or does it say, "media disconnected"?
If no IP address for you computer showed up with IPCONFIG then try this first: Power down the problematic PC and the router (if the other two working computers are plugged into the same power strip as the bad computer and router, make sure you power those down as well) Next, power on the router and let it run until all activity lights are up to par...Once the router is up and running,
then power on your PC to see if it will obtain and IP address automatically from the router.....that is, if your computer is configured for DHCP (obtaining ip addresses automatically from the default gateway, which is your router), which it probably is................
IF you are using a modem, the modem must be the first thing to be powered on...Next the router must be powered on and fully running, then the computer....in that order.
Once you've done this, look at your IPCONFIG stats. again and see if you've got your IP address back......
If your IP address is showing up and you still have no internet connection try this:
Open a command prompt and type:
ping www.google.compress enter, and see if you get a "reply" back... If you get a reply back then the problem may be in your browser.... Try resetting your browser to "default" or "factory" settings.
Are you sure that the switch you are using is actually a "router" and not a gateway? Reason I ask is because some people use the terms interchangeably, but the type of cable used to connect a PC to them are different types. Those other cables you tried, what type of cables are they? If you are connecting a PC to a router, a
crossover cable must be used. If you are connecting your PC to a gateway, a "straight" cable must be used. Although the two cable types look alike, there internal wire configuration is quite different..... Borrow a cable from one of the other two working computers for testing and see if it remedies your connection problem.....if you have not already done so......
If using one of the other two computer's cables doesn't work, make sure everything is up to par in Device Manager... make sure there are no errors next to "network adapters"
Now, after all this, you still have no connection to the Internet, try this: Restart your computer...Immediately, when your computer begins to power on, tap the F8 key and enter the Advanced Options....Then select "safe mode with networking".... When it boots try to connect to the internet and see if it works..