Laptop Wireless cannot connect

I realize this is such a basic problem. But there are specifics. Here is my situation: Got an HP Pavilion Laptop. The wireless worked for about a year. So I got a wireless usb adapter. It worked for about 2 or 3 months. No more connection. Right now I am using an ethernet cable. Both the built-in wireless see the router, get the information from it, report the strength of the signal, but after I enter my key they report that the cannot connect. Of course I've done all the basic troubleshooting like rebooting the router, rebooting the laptop, upgrading the driver, downgrading the driver. Nothing helps. I even connected the wireless usb adapter to a pc, and it functions with no problem. I believe it is something in the windows settings or registry that prevents me from connecting, so I would need some 'advanced' solution. Am thinking about restoring my laptop to several months ago, but decided to give it a shot with the forum. Thanks in advance for a tip.

Thanks, 2xg. Tried that, with no success. I think now there is a problem with the hardware part of my laptop. It didn't work after restoring to factory default. However, the wireless network adapter does work.