First of all a warning, this game is highly addictive. Seriously if you have a work deadline or something you need doing stay away from this, it will consume your spare time.
What a brilliant game! An absolute classic that set the bar for all strategy games to follow. I bought the gold edition which included the rise of rome expansion pack for £4.99. I initially had trouble installing it on Windows XP and you may find you need to go through a slightly different route to get it to install correctly but on Windows Vista it installs no problem.
Since it has been around for so long it will run like a dream on pretty much any computer thats around these days, you shouldn't have a problem even running the game on its maximum configuration.
The game play itself is superb. Whether you want to follow an historically based campaign or simply set up a custom battle, I guarantee you this will keep you occupied for hours. It should also be noted that when you do start to get bored/frustrated, there are many cheats available to help you get the most out of the game and then some (nuke troopers in ancient greece anyone).
How to sum it up? Its five pounds spent that will occupy and entertain for you just as much as something costing 6 times that. No real gore or violence or anything so pretty much suitable for any age group, easy to play, easy to see its mass appeal, simply a classic.