WIFI USB adapter will not connect to router

Happy New Year all,
I recently lost connectivity from the PC to the router via a usb dongle while the laptop will still connect wirelessly. Both the PC and laptop have Windows 7 home premium. The router is a Lynksis E2000. Thinking that the dongle had died, I purchased a new one, ran the installtion disk, installed the dongle and nada. I disconnected the modem and router, shut the PC down and rebooted everything. Nada. Interestingly, when either computer is shut down and rebooted and before accessing the internet, I have to enter a guest access password. I get that logon screen on the laptop but NOT on the PC. I have yet to run an ethernet cable from the router to the pc as i will need about forty feet to do that. I have run the trouble shooter on the PC and all it tells me is to go online for an answer. Any help will be greatly appreciated.

 

Yes, the pc has beeen setup for well over two years with a wifi usb adapter. Nothing whatsoever has been changed. Ability to connect suddenly lost. I am using the laptop right now. It was suggested that I run sfc/scannow as some files or the registry may have become corrupted. I reveive an error message that says I need to be logged in as the administrator. I AM the administrator!

 

First thing, trip, Windows 7 has a hidden Administrator account on it. Whatever software you're using to check the registry, you should be able to right-click on it and Run as Administrator. I'd recommend trying that.

Second, have you changed anything on the Linksys router? What brand of USB adapter are you using? Might be some driver issues if there's not a problem on the router's end.

 

I figuered out the problem. If anyone else has this problem in windows 7, try this; go to control panel, network and sharing center, local area connection status, properties. In my case, Comodo Internet Security Driver was checked. I unchecked it and rebooted. Voila! I now have internet access again. I have no idea how this happened as I made no purposeful changes to my PC. Thanks to all who offered help. BTW, after an hour on the phone with Comcast, they could not help me.