Here's a couple tweaks to try to improve performance for Nvidia users.
To improve your frame rates in game if you're using an NVIDIA graphics cards, open the NVIDIA Control Panel. Click 'Manage 3D settings' and in the 'Progam Settings' tab, click 'Add'. If 'Everquestnextlandmark64.exe' isn't listed, browse to it. Down in the feature box, set 'Power management mode' to 'Prefer maximum performance' and set 'Texture filtering - Quality' to 'High Performance'. This change barely reduces the quality of the in game graphics, but makes a HUGE difference for consistant framerates.
Playing in windowed mode significantly increases frame rates due to the smaller resolution of play. To enter windowed mode, press ALT + Enter. To return to full screen, simply press ALT + Enter again.