As I read your message, you bought the pc with 2 dual 512 sticks, added 
2 1gb sticks, and now replaced the 2 dual 512 sticks with 2 more 1 gb 
sticks.  Per the kingston.com website:
MODULES MUST BE ORDERED AND INSTALLED IN PAIRS for Dual Channel mode.
This system is configurable and may ship with either DDR2-400 
(KTD-DM8400/xx) or DDR2-533 (KTD-DM8400A/xx). These are compatible and 
can be mixed, however when mixed they will default to DDR2-400.
If 4GB is installed, the recognized memory may be reduced to 3.5GB or 
less (depending on system configuration and memory allocation).
Maximum configurations require a 64-bit operating system.
.
You may have a mix of memory that's not 100% compatible with the bios, 
motherboard, or the other 1 gb sticks already installed..
You can also try the dell.com website.  If you enter your pc service 
number, you can get more detailed info from their site.
.
Paul Hachmeyer

Trey Holm wrote:

>Is there anyway someone could tell me how to determine why Windows is
>not picking up new RAM I just installed?  I have a Dell Dimension 4700
>that came with  2 dual 512 sticks.  Later I put 2 1G sticks that Windows
>picked up.  I have now replaced the old 512's with 2 1G sticks.  The
>BIOS setup picks the new sticks up, but when in the properties menu
>under My Computer, it shows the total from the old configuration.  How
>do I determine whether the sticks or bad or Windows is the problem?
>
> 
>
>Thanks,
>
>Trey Holm
>
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>
> 
>

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