herryFE:
I've found that the stock answer to these types of questions on this board is to "upgrade your system." "Buy a new this or a new that", -- usually the component/brand the poster uses.
Of course that will work; it's often a valid answer.
But....
Given your question, here's what worked for me:
Click on the VIDEO button on the clipboard you get when you start up AH.
I have the "Enable mip mapping" box and the "Disable Palettized Textures" box CHECKED. I have absolutely no clue what these mean in layman's terms, but someone else suggested them in another post awhile back, so I tried it. My frame rate increased. (It may have been a coincidence, but it can't damage your setup to try it. If someone can explain these functions to an old fart, I'm interested.)
Under 'Video Res.' on the left, start with the lowest resulution (at the top).
Under 'Color Depth', start with 16 Bit.
Under "Max Frame Rate," start with Unlimited.
Run AH (online) and see if it improves. If so, then you can experiment with clicking the next box down in each of the areas until you get the best possible video/play quality at a framerate that's acceptable to you.
I've found that it's pretty much a 'trial-and-error' process for non-video-gaming-savvy folks like myself.
Splash1