Are there any obsticles in between the computer down the hall and the router?
The wireless-n router should reach that far without problems.
Does the wireless network show up at all when you search for them?
Try repositioning the router and wireless network card antena. This can make quite
a difference even with small adjustments.
Also, have you tried moving the router next to the PC and then connecting?
If it doesn’t then it could be an issue with the wirleless network card or card driver.
It may be that there is a router close by which is using the same frequency channel which
will result in problems with some items trying to connect, especially if the signal strength of
both networks happens to be overlapping at the point where your computer is sited.
You can change the channel by logging into the admin page on the router, going to wirless settings, and chnaging the channel there. The default channel is 6, so try 1 or 8, or something similar.
You may not get the rated speed by doing this (upto 300 mbs), since the rangemax routers use multi channel broadcasts to achieve the enhanced speed, but to be honest you won’t notice if your just connecting to the internet.