If I currently have CS4 installed and Prospect installed. What do I need to do, in order to install CS3 and have everything setup correctly?
Like do I need to uninstall prospect? and reintall prospect after installing CS3?
Do I need to uninstall CS4? then install CS3 and install CS4 over it?
can they coexist?

This is what I did. I am using CS3 and CS4 with Cineform.

I un-install Cineform First.
Then Install CS4, do all the updates etc.
Then install Cineform.

What Version of Prospect? Ver 3.x or Vers 4.x?

I already have CS4 installed, worried that if I install CS3 over it, it might mess something up. I have V4 prospect

Ok, When you install CS3, it should be fine, but frankly, CS3 does not work that great with v4.x of cineform. I have lived through this the past 6 months. I use just went back to Premiere CS3 and Cineform 3.x code. It works great.

Yesterday's update, 4.05, IMHO, made Premiere CS4.1 usable for me. I just bought my uprade to NeoHD 4.05 and after testing all last night, I going to move to CS4.1 and Cineform 4.x.

I know prospect is not done yet, but the Cineform is getting real close now.

Ok, When you install CS3, it should be fine, but frankly, CS3 does not work that great with v4.x of cineform. ...

CS3 and v 4.x of Prospect 4K work VERY smoothly for us, and so far, no probs. So it might just depend on what your setup is. At least with Premiere, we've had very smooth sailing.

But like Andy said, you might have a working version with release 4.05 and next few. Hang in there