Sounds like your connected to someone elses wireless for one. Try this.
1. Click on the start button on the bottom left of your screen.
2. Look for run, start search, or search program and files (Depending on your OS)
3. Type in CMD and press enter on your keyboard.
4. Type in IPCONFIG and press enter.
5. What is listed as the default gateway of your wireless adapter?
If its 192.168.0.1, try this, when online wireless, unplug the power from your Dlink router. Still online? If so, proofs without a doubt your connecting to someone else router. If you go offline when you unplug the router, have a 192.168.0.1 but can't access the gateway, probably either a block on your PC or the router. First thing to check is connect the laptop wired, and still see if you cant connect to the gateway. If you can wired, but not wireless, could be blocking wireless access some how. If you can't either, then I don't know, but its probably something with your PC.