Playing IWD1. My graphics card is a Invidia GeForce 8600M GT. I have 4 GB RAM, so I'm sure my machine is fine to handle it.

It loads really fast, and generally is OK off the bat. But after a while I'll have periods where it drops to like 3-5 FPS (estimating) and not only when there's a lot on screen. Just moving around, and even the cursor slows if my party is standing still. I went into the driver controls and tried turning everything off... Nothing seems to help. Am I just out of luck?

It goes slow, then speeds up again, and repeats. No seeming reason to it. It's so bad it's unplayable. Any ideas what to do?

My drivers are up to date. Should I try rolling back the driver?

Try using the config utility included in the game directory to enable hardware 3D acceleration. Alternately you can change the parameter in the game's main INI file.

I'm playing under Vista, and have the same problem with an ATi 4850, and I used this trick under XP for other games too. But another solution is possible (very useful under Vista / 7, though it may help with XP too, maybe with better performances) :

Download the Microsoft Application compatibility toolkit, and then launch the Compatibility Administrator (in Admin mode). Right-click on New Database in the list, Create New Application Fix, fill the first part, uncheck Windows compatibilities ("None") in the second. Then search for "ForceDirectDrawEmulation" and tick it. Skip the last part, close the window. Then save the database somewhere (preferably at the root of the game's directory), then right-click on the barrel (or go to File [...]) and Install it. You can eventually close everything.

From now on, the game should run with forced DDraw, without changing the general 3D parameters. And from what I saw on Planescape, and now IWD2, everything runs smoothly (a steady 30 fps). I hope it will help ! (it may also help with on-screen artifacts, or others bugs, even more if coupled with D3D Windower).

This solution works for my Windows 7 AMD as well.