click start > run > type "regedit"
go to HKEY_LOCAL_MACHINE > SOFTWARE > PlayOnlineUS > SquareEnix > FinalFantasy XI
In that thread, modify entries 0003 and 0004 to the texture resolution you wish to use. Hit the Decimal radio button and enter in a value between 1 and 2048 (depending on the strength of your video card). That will make everything look nice and crisp. Make sure you are logged out of ffxi when you do this, or the settings will be overwritten.
If you want to tweak further, entries 0001 and 0002 is your screen resolution. You can set it to a non-standard resolution like 1280x720 if you play on an HDTV and so on. Then you just switch the aspect ratio in the config > misc menu of ffxi. If you're using windower, you'll need to open windower.ini in your windower folder, and edit "X Resolution=" and "Y Resolution=" settings in order to change the screen resolution, this should be done in addition to the registry tweak, to keep continuity across the board. If you stop using windower, be sure to enter the registry again and restore your settings to your monitor's preferred native resolution
**(often 1280x1024 for LCD monitors, 1600x1200 for CRT monitors, and anywhere from 1280x768(or 800), 1680x1050, or 1920x1080 for widescreen monitors.)**