And you also need a big-time machine to experience battles in all their glory. Conflicts in Medieval II are so massive that you should have a top of the line Pentium IV or equivalent AMD CPU with a couple of gigs of RAM and a 7800-class video card. Anything less and you need to turn down visual settings, which leads to some ugly jaggies and jittery frame rates.
But don't consider the tech demands as a reason to avoid Medieval II; think of them as a reason to upgrade your computer. Since this is one of the best strategy games of the year, and arguably one of the best ever, you won't regret shelling out the moolah.