P5KC + Intel Q9300 = sloooow

greetings fellow geeks

I've just bought this lovely new Intel Core 2 Quad 2.5ghz Q9300 processor and an Asus P5KC board to put it in.
I ran the mandatory bios update to 1105 to make the board fully support my cpu, and then happily reinstalled windows xp as one would normally do, when changing mobo.
I also got 2 sticks of ram from a friend of mine, KVR800D2N5K2/2G. They are "value" class from Kingston, but till about a week ago, they have served his machine well, till he upgraded as well, so I'm not guessing the RAM is the problem.

Till now, my benchmarking tool has been running the performance test in Company of Heroes: Opposing Fronts, with EVERYTHING to max, except we're both using Shader Quality = High (running XP), Antialiasing = 8xQ CSAA and Terrain detail is set to High (ultra not available on neither of our machines).

Overview of our hardware and testscores

My friends hardware:

• CPU: Intel Core 2 Duo E6600
• Mobo: Asus P5E-VM HDMI
• RAM: Corsair XMS2 (not sure of the specs)
• GFX: GeForce 8800 GT

My friends score on CoH: OF performance test:

• Average FPS: 50
• Maximum FPS: 57
• Minimum FPS: 3

My own hardware:

• CPU: Intel Core 2 Quad Q9300
• Mobo: Asus P5KC (BIOS 1105)
• RAM: Kingston Value RAM (KVR800D2N5K2/2G)
• GFX: GeForce 8600 GT

My own score on CoH: OF performance test:

• Average FPS: 22
• Maximum FPS: 44
• Minimum FPS: 10

Now my question is, why the hell is my machine lagging so much? I know my HD is pretty fragmented, but not so much is should have a performance hit this big.
I've tried using this guide http://www.hardware.info/en-UK/pro [...] R2800_kit/ to set the RAMs CAS etc, right at 400mhz, with no performance change at all.
CPU-z says everything is as it should be, regarding my CPU (checked with some other peoples CPU-z results).
Now, I'm hardly novice when it comes to computers, but I must admit I've never tried fiddeling with the voltage etc in the bios on my machines, but maybe this board just dosent know how to "treat" my processor right = i have to set up the voltage myself, but I have no idea how, and all guides ive found till now, hasent seemed specific enough for me.

Hope the "braintrust" here can throw some suggestions my way

Have a nice weekend
-Bitcrusher

yeah change the name of your post to "8600gt fail vs 8800gt".