I've had memory from the same manufacturer with the same part number with different branded chips attached.  There are differences in cas, latency and other specs on a memory stick.  Try downloading a utility such as SiSoft SandraLite (there are many others that identify system components) that actually reads the specs of the memory in each slot.  Then you can compare the 4 Kingston sticks to see how well they match, or not.   DDR won't function if they are a poor match.
Paul Hachmeyer

> Date: Sat, 25 Oct 2008 17:55:46 -0700
> From: [log in to unmask]
> Subject: [PCBUILD] RAM slows Vista
> To: [log in to unmask]
>
> My system is slowing down when I add more RAM. I upped it to 4 GB and
> everything slowed measurably.
> The system is:
> Intel Core 2 6400 @ 2.13GHz
> Intel DG965OT MB
> 2 GB DDR2-533 SDRAM (Hyundai)
> NVIDIA GeForce 8800GT 512 MB
> Vista Ultimate, SP1
>
> At first I added 2 Kingston Value RAM DIMMs with the original Hyundai DIMMs,
> then tried 4 KVR's to make sure it wasn't different manufacturers. I'm
> beginning to wonder if there's not a problem with DIMM slots 2 & 4. As soon
> as I returned to the original DIMMs, everything was fine. Am I missing a
> BIOS setting?
> When I have a minute, I'll switch and just use slots 2 & 4 to see if that
> replicates the problem.
> Thanks for any advice you might have on this.
> Chuck Finnigan
> [log in to unmask]

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