In order to access the secret cow level, you must defeat Baal. Then, make a game for the difficulty you just beat him on (e.g. If you beat Baal on Normal, make a game with Normal difficulty). Go to the Rogue Encampment, put Wirt's Leg and a Tome of Town Portal in a Horadric Cube, and a portal leading to the secret cow level will appear.
Note: If you want to continue to make these portals to the cow level, do NOT kill the King Cow. If you do, you can no longer access the secret cow level from that difficulty.
While in game, type ''soundchaosdebug'' (without the quotes).
It plays every sound and NPC conversation in the game.
To turn it off, just type it in again.
Go into a game. When everything loads you press enter to open the message space. You then type in "/fps" with out the quotations. Then in the top left hand corner it should show: Frames per second, Ping, and skip.