Wired Keyboard and hot key confusion

I just recently purchased a newer mac pro, version 3, that was running Lion. I bought a wired keyboard for the computer and it all worked just fine (all the f keys worked for their displayed purposes). I just did a clean install and reverted to Snow Leopard as most of the programs I use are run on Snow Leopard except now I'm experiencing some problems. My f keys are not responding as printed. For instance, the f12 key which should increase volume, brings up the dashboard widget. Now I heard that is I unchecked the box labeled "Use normal fn functions" from system preferences it would resolve this, however, checked or unchecked f12 STILL just brings up the Dashboard widget. Also, I heard hitting Command F5 would resolve this, but that just brings up Voice Over. So my question is, how do I go about getting my keyboard to function correctly again?

Thanks!!

The newer Apple wired aluminum keyboards require at least Snow Leopard 10.6.8 in order to function properly. Update your version of Snow Leopard to 10.6.8.