Apple wireless keyboard is outputting an " character when I expect an @ character I just bought a Mac Mini and a wireless apple keyboard. Whenever I type Shift+2, expecting the @ symbol to appear, I get a " character instead. How can I diagnose the problem and correct the mapping so Shift+2 produces the @ symbol as expected?

Several other Shift keys in that row are also wrong:  6 is &amp;, 7 is ', 8 is (, 9 is ), 0 is 0.
For some reason your mini thinks the keyboard is a JIS (Japanese) keyboard "type".  This note might help:

http://m10lmac.blogspot.com/2009/12/fixing-keyboard-type-problems.html