Yes, you need pokertracker, but PAH only works with PT2 (as it clearly says on the download page:
http://www.pokertracker.com/products/PAH/download.php) and PT2 is no longer for sale now that PT3 is out.
PT3 has it's own built in HUD, so you do not need PAH for this.
Please try out the trial version of PT3 if you are playing at one of the
Supported sites.
http://www.pokertracker.com/products/PT3/download.phpIf you are playing at a site which is not yet supported, then you can try the trial of PT2:
http://www.pokertracker.com/products/PTH/download.php.
If you decide you want to buy PT3 (or PT2) then please pay full price for PT3 (rather than using your PAH discount) so that you get the free PT2 and PAH licenses, then if you create a ticket on the
Support system you will be refunded the cost of your PAH purchase.