or Hold'em Manager (http://www.cardschat.com/f13/hold-em-manager-116708/)
People who play more than half a dozen tables were having trouble with PokerTracker 3 so some of them have moved from PokerTracker to Hold'em Manager.
I haven't used it Hold'em Manager, but I thought I remembered hearing that it's not as good as PokerTracker for tournaments.
Not only will both programs keep track of your statistics (wins/losses by hands and positions and levels and and pretty much anything else you can think of) but they both come with HUD's (Heads-Up-Displays) that will show your opponents stats at the table. Those stats are invaluable for multi-tabling.