Go to <Connections> from the Start menu and highlight your wifi adaptor. Then chose <Change settings> in the left side bar. This will allow you to access many of your wifi settings. Go to the the second tab on the window that you've opened (labelled Wireless Network) and make sure you've selected 'Use Windows to set my Wireless Network'. From there you can also select preferred networks.
In the 'General' tab make sure you have TCP/IP ticked (others will be as well, some you need some you don't but leave them alone). Close the dialogue box
Try again logging onto your WiFi again.
One confusing issue is any utility that came with the wifi card. You should either chose 'let Windows control my wireless' - most peoples preferred option, or the card utility but not both. Ideally you should completely delete the unused utility.
Just one final thought - can you open the laptop case to make sure the wifi antenna is connected? Many laptops have a removable hatch cover on the base and you should be able to see. However other laptops need to be dismantled to look. Depends which you have.