The sites that use Microgaming software (Prima Network and Ladbrokes) and the PokerRoom/Ongame sites (PokerRoom, Hollywood Poker, etc) all write hand history information to a database file on your computer. This file is in the form of a SQLite database file which means special drivers are needed in order for Poker Tracker to connect to the file and pull the information out of it so that the hand histories can then be stored in your Poker Tracker database.
If you get the error message that the SQLite drivers have not been installed then you can download this file...
http://www.pokertracker.com/products/ol ... bc_new.exe
And then double-click on the file after it downloads to install the required drivers.