Laptop router connection

[#1]

A Friend of mine has a laptop running windows 7 but each time he comes to log on there is no connection between the Laptop and the router although it is clearly showing that there is a connection when looking at the icon in the task bar, it is also showing that the laptop is connected to the correct router.
By going into the network centre and selecting the router and then diagnose the router connects and works fine in that it does not drop the connection at any time.
The signal strength is showing 4 bars out of 5.
So for some reason the laptop is either failing to remember the setting or something has not been set up correctly ?
It's a bit of a pain having to go through this procedure every time the laptop is switched on and he  would be grateful for any advice on this.

[#2]

Hi gleneagles,
What error is it that the connection diagnostics tool finds? Just thinking that might be worth looking at, as if it finds the problem and fixes it on the laptop by the sounds of it that is where the error must lie.

[#3]

When trying to connect it comes up as unknown network but on the list of routers shown the correct one appears and is shown as connected.
Going on to network the correct router is listed but has to be selected before the program runs through attempting to repair problem which eventually ends in that it fixes the problem but during the process no error messages come up.
I'm not sure if the connection diagnosis tool is the same one as used to correct the problem but if so I am unsure where / how I could get it to identify what the problem is.

[#4]

got a bit further with this.........
Messages shown are.........  Does not have a valid IP Configuration
IPV4  connectivity Internet
IPV6  no network access

[#5]

That could mean the router is not assigning an IP address to the pc.
Try to renew it.
Start> Run> cmd> in the box put..  netsh int ip reset reset.log > enter and wait then
                                              put..    netsh winsock reset catalog > enter wait and reboot the pc