Mixing memory can work but not always. Since you are getting 2 new 1 GB 
sticks, just use those in slots *1 & 2 *and forget using any other(s) 
that are in there now. Since you plan on ordering Dell memory from Dell, 
there should be no problem with compatibility. 2 GB seems to be the 
sweet spot for Windows XP according to recent reviews I've read.

The on site instructions for removing and replacing the memory are 
fairly good. Before trying to install a memory stick just make sure that 
the small slot in the memory stick lines up with the raised ridge in the 
memory slot. You will find that changing memory is easy though it can 
take an unexpected amount of force on each end of the memory stick to 
have it fully seat itself to where the retaining tabs move into place. 
Remember to ground yourself on the case before working inside the case.

Consider also that, unless you are using your computer for some memory 
intensive applications, a 1 GB stick of memory will perform well for 
normal usage. This could save you some money for now especially at the 
price of Dell memory. You can always add a second 1 GB memory stick in 
the future if you needed it. If only installing one memory stick at this 
time, install it in slot *1*. The second one would then go in slot *2*.

I hope this helps.

Tom Mayer

[log in to unmask] wrote:
> _http://support.dell.com/support/edocs/systems/dim8400/SM/parts.htm#wp1058792_
>  
> (http://support.dell.com/support/edocs/systems/dim8400/SM/parts.htm#wp1058792) 
>  
> I am in a dilemma and need  help.  I have a Dell Dimension 8400.  Here are my 
>  specks::
>  
> Processor-----------------------Intel (R) 4  CPU 3.00GHz
> Memory-(RAM)-----------------256  MB
> Operating-System---------------Microsoft  Windows XP Home Edition
> Operating System  Version------5.1.2600
>  
> I was trying to format  cause I had gotten that blue screen, but it would 
> never go all the way through..  When it was copying the files.. it stopped midway 
> and I did this three  times.  I finally called a tech here to come see what 
> was wrong.   After fooling with it for 2 hours, he pulled a memory stick out 
> and the  formatting was able to go on through.  He said I needed another memory  
> stick since that one was bad which he said he would order for me.  He never  
> did, and here I sit with a slowed down computer, but at least it  works.
>  
> I got online with a Dell  tech who sent me the above instructions on how to 
> install the required memory  sticks.  (The Tech here said he would order me 2 
> GB of memory - 1 GB each  to replace two that were in there.)but I have not 
> heard from him  since.
>  
> Now, in reading those  instructions Dell sent me, it says this in there 
> (which confused me so that I  don't know what to do now mainly cause I am not 
> familiar with the innerds of a  computer)
>  
>  
> <<< If you  install mixed pairs of DDR2 400-MHz (PC2-3200) and DDR2 533-MHz 
> (PC2-4200)  memory, the modules function at the slowest speed installed.  
> Similarly, if  you install memory modules with mixed CAS Latency (CL) rates, the 
> modules  function at the speed and CAS latency capablilties of the slowest  DIMM.
>  
> Be sure to install a  single memory module in DIMM connector 1, the connector 
> closest to the  processor, before you install modules in the other  
> connectors.
>  
> NOTICE:  Do not  install ECC memory modules. >>>
>  
> Since the tech never came  back to the house to fix my problem, I'm having to 
> do it myself.  I need to  know what I am to do and exactly where those memory 
> sticks are and which one or  ones I am to remove when I install the two new 
> 1GB ones when I buy  them.
>  
> Now.. I had gotten back  with a second Dell tech and asked him what to do, 
> but he was as puzzled about  this as I was.  Therefore I got no information from 
> him in this  regard.  I just dont know if I am to take all four of those 
> memory sticks  that are in there (or does this computer only have 2 in it) or just 
> take 1 out  and replace it with the 2 news ones I will be getting..  but the 
> 1 and 3  seem to be in one slot and the 2 and 4 in another.  I am totally  
> confused.  Thanks for your help.  Harriet
>
>  
>
>
>
>
>   

               The NOSPIN Group Promotions is now offering
                 our special coffee mugs and mouse pads
              with the PCBUILD logo...  at a great price!!!
             http://freepctech.com/goodies/promotions.shtml