The following settings have previously been posted by "Phoenix" in 2005 (thanks and appreciated) however I still have a lot of blockyness in my graphics,my specs are as follows:
GPU Nvidia 8600 GTS@1280x1024 XPSp3 4gb RAM
Zenack settings
Texture Memory 16MB
Resolution Try high res
Refresh rate (monitor frequency)
Vertical sync By app (default)
Mipmapping Force trilinear
Load bias 0.00
Anisotropy None
Gamma 1.3
Limit feature set Most fancy shaders
Render to Own window (default)
Thread policy Classic (default)
Resolution limit 1280x1024

Nvidia Control Panel Driver Settings:

Anisotropic filtering Application-controlled
Antialiasing - Gamma correction On
Antialiasing - Mode Application-controlled
Antialiasing - Setting greyed out
Antialiasing - Transparency Off
Conformant texture clamp Use hardware
Error reporting Off
Extension Limit Off
Force mipmaps None
Maximum pre-rendered frames Use global settings (3)
Multi-display/mixed-GPU acceleration Single display performance mode
Texture filtering - Anisotropic sample optimization Off
Texture filtering - Negative LOD bias Allow
Texture filtering - Quality Quality
Texture filtering - Trilinear optimization On
Threaded optimization Off
Triple buffering Off
Texture filtering – Anisotropic mip filter opimization Off
Vertical Sync Force on

I missed this one. I noticed a big mistake I made in describing the Glide Wrapper settings. The resolution must be set at 1280X960 to keep to original aspect ratio. Otherwise, the textures get messed up. I reupped the files in a more recent post. Check to find them there.

I once owned an 8600GT, and I don't recall whether I could get it working on that GPU, but it's worth a shot.

I had the 8600GT (now have the 8800 GTX), and I remember it worked fine with this sim.

I meant the glide wrapper (and thus, the resolution change). I've owned many Nvidia cards and they all behave differently with each glide wrapper; some didn't even work in Primary Display Driver mode -- the 8600GT was one of them. It just gave me lots of troubles in general, this sim included.