when i check the available connections, i can find the router with full signal, but after typing the password and click the connect button, it said unable to connect
sounds like an association problem between your router and wireless adapter, as said before hard resetting your router could help.
dont ever rely on microsoft troubleshooting,probably the biggest thing i hate about all windows stuff the troubleshooting of everything sucks and doesnt help much at all.
My Computer
Computer Manufacturer/Model Number
Custom Build
OS
Dual Boot : Windows 7 7264 X64/Windows Vista Ultimate
There are a couple of ways on most routers there is a button that resets to factory defaults. If you dont have that unplug and leave unplugged for abt a minute
Tip when hard reseting the admin and password revert back to what it was from the factory (admin, password)