Hold in the reset button on the back for 15 seconds, let it reboot, and check that all the correct lights are on and are steady (as per the manual). That will make sure the router is set the best it is going to be.
Question: has it ever worked on the machine you are using with your existing wireless adapter?
Is the wireless adapter built-in, or is it one of those USB dongles?
Can you either get the router tested at a store or test it with a laptop you KNOW works on other available networks?
Does your laptop find the router at all?
Can your laptop find other routers?
Once you can safely say "my laptop definitely works and the Netgear definitely doesn't" you've got a case :)