Random slowdowns every 10-15 turns

[SK138]

Playing Civ 4 or Colonization I am getting random slowdowns every 10-15 turns. I played the game with the task manager performance monitor open on another screen to try and see whats happening. My memory usage stays around 1.4 to 1.6 GBs out of 2. The problem I am seeing is the CPU Usage which is around 40-60% when the game is playing normally but then shoots to 100% when the game slows down. It will slow down basically to a stop for about 5-10 minutes before going back to normal and this keeps repeating itself. It's not even a late game problem. I've had Civ 4 work on this computer before with no problems and I just reformatted to see if that would help but I am getting the same problem.

I have Windows Vista Home with:
Dual Core2Duo 1.83 GHz
2 GB Memory
Radeon X1400 128 MB Video Card

I have installed the game on my older computer and it has:
Windows XP
Pentium 4 2.40 GHz
1.5 GB Memory
Radeon 9600 128 MB Video Card

The game works fine on my older computer which is about six years old with less memory and an older video card.

Does anyone know what my problem could be? I have attached my dxdiag.txt file for anyone that things they can help.

 

[Dale]

Virus scanner...... small pagefile thus Vista has to keep scrubbing the cache...... some background process kicking in every so often....... CPU over heat........

Take one out of the hat. There's a million reasons.

 

[SK138]

I don't have any virus software running and I have set the page file to 5 GB and I still have the problem. I am not sure which background process if any would cause it. The overheating issue sounds like a slight possibility since it is on a laptop, but like I said before, I've had the game running before with no problems.

 

[Dale]

If the games used to work, and now have stalls then it's gotta be something that's changed between then and now.

 

[SK138]

I am not sure what else could change, epsecially after I reformatted.

I tried the windows compatibility thing to make it run like its using XP and that definately helps. I also just installed Windows 7 so I am going to try that out.