Well, is the laptop and phone being placed in the same room, same orientation? You know a laptop is likely to have a bigger antenna. Perhaps re-position your router to another spot away from the wall it is near.
Did you take the back off the phone? Is the back of the phone seated properly?
Settings | Wi-Fi, press the Menu button and choose Advanced Wi-Fi. Make sure Wi-Fi signal weak is not checked so it disconnects upon a weak signal. I guess I would also make sure I unchecked Internet unavailable.
Try rebooting your router. Does it help?
Download WiFi Analyzer and make sure your router isn't on the same or near the same channel of another router. Change the channel of your router if it is close or overlapping some neighbor's router. Reboot router again. Does it help?
You could always try backing up your important files / settings, and doing a Factory Data Reset if nothing else helps but maybe your antenna in your particular phone is not that good. Hard to say.
