As you've posted in the wireless networking forum, first suggest you try to optimise your reception and avoid interference.
1) raise the router above furniture level
2) Experiment with channels (some will work better or worse depending on your environment)
3) If you can detect strong neighbouring wifi, use a channel 5 stops away from strongest.
4) Relocate cordless phone base or video sender etc.
5) Be prepared to move the computer (or at least turn it so your body is not between the router signal and the wireless adapter's antenna.
Of course the issue may also be that you are simply not connected -- I would have a look at the literature which came with your router for how to access the user setup screens via your browser.
Once in check wireless mode matches your wireless adapter's mode and try turning off wireless security until you get a reliable connection.