Burning cd from iPad?

I have an iPad1. I'm a dj and I bought some tunes from iTunes because it's the only place they are available legally. However, I can't burn the tunes to cd.

I've transferred the tunes to a pc, created playlists, have decent cd-r's, but when I click File to find the Burn To Cd, it's not there. When I look on the pc the tunes have a lock symbol on them. Why is this?

I've bought the tunes, I'm not trying to rip anybody off ... If i was, I would have just downloaded the illegal versions. I just want to burn the tunes I've bought.