I belive the best bet IMHO, is that giving someone a I-Tunes or Napster card as a gift and let the person receiving the gift card download the song (s) themselves. Buying a Cd for them would be the other option.
Then again giving or selling them a MP3 player with tunes already loaded in the player by you, would be illegal, as well as selling a computer with loaded tunes by you, too. Unless, of course it was YOUR music you composed created, wrote and performed.
However buying a MP3 player from a store with tunes preloaded by the manufacturer in arrangement with some record companies to promote new music, is 100% legal.
On the other hand, selling or giving away a CD coin operated jukebox with Cds loaded in it,... is legal, just as if one sold the same CDs used separatly. Same being selling a record player with a box full of vinyl. or a tape player with a box full reel to reel tapes or cassettes or 8 Tracks. (as long as all the recordings were legit to begin with).
Now if you gave or sold someone a computer with a P2P application already installed, that might be illegal....maybe for you.
If you give or sold someone a computer, then they put a P2P app on there and download some illegal stuff...its their problem.