How Can I Make My Game Play Faster?

I Bought Quake 4 Which Is A Really Good Game So I Decided To Play It Online And Was All Pumped Up. Then It Came Down To It. I Get In The Board And My Gameplay Is Really Slow. Its Lagging Really Bad. What I Did Was Turn The Quality Down To Its Lowest And It Helped Jus A Lil Bit. I Cleaned Some Stuff Out Of My Computer To Free Up Some Space. Which Also Helped A Lil Bit. I Figured My Gameplay Would Be Really Great Since I Have DSL Extreme. Supposed To Be 50 Times Better Than Dial-Up But I Checked My Bandwidth Online And It Said It Was Only 30 Times Faster. I Thought This Will Be Good Enough To Play With. Its Just Ok....Not As Good As I Want. Can Anybody Give Me Any Ideas Or Tips In How To Make My Online Quake 4 Gameplay Faster?