That means your video card doesn't support TnL. FFXI doesn't require you to have a top of the line system, but it (like many games for PC) require you to have at least somewhat decent specs. You can pick up a cheap video card that'll run it fine, these days.

Edit: And at least it's not like Vanguard, where you need to have a really beefy computer, plus 25GB or so free space.