Somewhere I saw a description of how to use a USB nuber pad to respond to FSX ATC commands. Anyone remember where it is?

It wouldn't be that hard.I don't have FSX, but the idea should be the same.When the ATC window is open, you have 1 - 0 options.Plugging in a USB number pad would allow you to put that pad in a "handy place" rather than having the WHOLE keyboard there.Then, when the ATC window is open, you simply press the 1 - 0 keys for reply to their request.This also has drawbacks too, but it has been so long now, I can't remember them just now.Thing is: The pads are not that expensive. Get one, plug it in and see if you like it.Sorry, that's the best I can suggest.

Unfortunately what Flying Dog suggests won't work out of the box.The numeric rows on top of your standard keyboard (from left to right) are treated differently by the sim as the numeric keys on the keypad. The latter won't work with ATC. There is a solution though.Some time ago I discovered a tool called hidmacros (just Google it) and it will convert the keys to anything you want. The great thing is that this tool will allow you to connect several keypads and make a different translation table for each.This tool was written for FSX and can even send commands to the sim through simconnect.