You plugged an Audio Technica AT2020 into your computer but there is no sound?
If you have an Audio Technica AT2020 and you plug it in using a typical microphone jack it will actually work (just super faintly). This is because the Audio Technica AT2020 requires PHANTOM POWER (meaning the cable must power the microphone, so an XLR to microphone jack WONT work).
To get you Audio Technica AT2020 working, you will need a XLR F5 to usb cable. This will provide power to the microphone and also serve as the connection to your computer.
NOTE: Make sure you plug it in to a USB port which has power most on your computer will, but it is pretty common that some USB hubs don't carry power. I recommend plugging your Audio Technica AT2020 directly into the computer.
If this isn't the problem, make sure you have the microphone correctly selected under the sound control panel in either control panels (Windows) or the sound system preferences pane on Mac OS X.
Also make sure your microphone is not muted and, (yes this will seam obvious) make sure your speakers are plugged in, turn on, correct configured and not muted. Simply playing some music will confirm this (it's not uncommon that someone will thing their microphone is not working because they can't hear sound when playing back a recording an it is actually the speakers at fault).
I hope that helped you to get your Audio Technica AT2020 working.