One of the nice things is that if your computer was purchased in the last couple of years, it's probably current enough to play many of today's great PC games. Unlike console games that run at a specified graphics setting so it looks the same on every system, players can turn different settings on or off, or make them higher or lower so they run as well as possible on the computer.
On the bottom or back of the retail packaging of PC games there's something that tells you the minimum specifications your computer must have to run the game.
It may require a couple of hundred dollars to upgrade certain parts to play the best games with the prettiest settings, but you may get more use out of your computer than you would a new PlayStation 3 or Xbox 360, so it's certainly something to consider.
Bottom Line: Getting into PC gaming can be expensive if you don't already own the equipment, but if you do it's a no-brainer. Your computer is capable of playing some of the best games out there and with a new graphics card every couple of years, you can stay on the cutting edge.