Well, here are two tips to help out.
1. Start -> Run -> "msconfig". Click the startup tab. Disable everything. Restart your computer.
What this does is prevent programs that would usually start up with your computer and run in the background from starting each time you reboot. This is the main reason a lot of peoples' computers are terribly slow because when they start the computer, they have AIM, Limewire, McAfee, Norton, Bloatware, all running the background using precious resources.
This actually works pretty well.
Forgot to mention, there are settings ingame in the configuration menu that'll help reduce lag such as turning off shadows, extended drawing, dust effects, and physics. Edited, Sep 17th 2010 11:39pm by EpedemicOptikz
FFXI(retired 04/2006): Epedemicoptikz, Phoenix Server, 75 SAM/NIN/WAR