CoD:Bo is very CPU intensive, as well as more GPU intensive than CoD4 and MW2. Vista hogs RAM,
but 4-6Gb should be fine for a 64 bit os. My specs are as follows:
Quad Core i5-750 2.6Ghz (Oc'ed to 3.54Ghz)
Arctic Freezer Xtreme Rev2 CPU cooler
Gigabyte HD 5870 stock clocks
I had fps drops down to 50 fps when I first installed the game, though after overclocking my
CPU I never go under 95 fps. A quad core with clock speeds around 3Ghz+ is a must for games like
CoD:Bo, Bad Company 2 and Arma2. On top of that you will need a decent GPU with 1GB memory to run
resolutions @ 1680x1050 and higher. The 6850 is a mid range card, though I can just about
guarantee a 10-20fps jump if you raise the clock speed of your CPU. Just bear in mind that
the Core 2 Quad series run hot when overclocked so you may need an aftermarket cooler. 3Ghz would be an ideal sweet spot.
Try raising the CPU frequency in small increments, boot to windows and run Core Temp
to monitor temperatures and stress test with Prime 95 until you get the desired fps increase. If you do not feel confident,DO NOT PLAY WITH CPU CLOCKS!
Especially if the heatsink and fan are full of dust.
Also do some research on your motherboard, you may find that it limits how you overclock and how much.
For small overclocks like this you should not have to touch voltages, raising voltages can lower
temps and make it more stable when overclocking, but is usually the first thing to kill a CPU
or motherboard. Just raise the base clock speed, run Prime 95 for at least 20 mins and watch the temperatures.
As a general rule 80+ degrees C is bad, over 90 can kill CPU/Mobo. Aim for around 70-85 degrees C
maximum with the Core 2's. Although you may already be hitting that under load now so be careful.
Research is the key. Find the limitations of CPU and steer clear of it, monitor temps and grab an
aftermarket CPU cooler for under $100. Even Corsair offer water cooling for under $200 now.
Here are some links if you do decide to go down that road:
Prime 95: Stress tester. http://www.mersenne.org/freesoft/
Core Temp: Temperature monitor. http://www.alcpu.com/CoreTemp/EDIT
Also to fully answe your question some users do have trouble with win7, but I run both in
separate partitions on my HDD and fps are around the same. I just don't like win7 lol. Desktop toolbar annoys me.