Where to install new DRAM memory stick

I posted a while back re: distortion to sound and we eventually came tot he conclusion that I needed a new machine or a clean insall of Windows. That is still my medium-term aim,  but my schedule is simply too full to take time for this right now.  Last week the machine wouldn't power on - right in the middle of a work project with a lot of data on the hard disk - and luckily they re[aired at for a prettt small fee, and at the sane time confirmed that the video card was faulty and the machine was running from onboard video, and that a 2Gb memory module ha was not finctionining.  Crucial have shipped a free replacement module to me and I want to install it now, but need to ensurer I am inserting it in the right slot.  I have a Dimension 5000 running Windows XP, SP3.  Can any one help me with this please? PS Doesn't this after all  point to  the blown memory  being the key to the problems discussed in my last thread? The machine is running now slower than it has done for months  which rather indicates that the memory loss  is longstanding - which in turn begs the question of why the memory test found it to be OK.

This page HERE will help you, also the rest of your manual is HERE.

Thankyou for the links.

I have now installed the DIMM and find that the system is no quicker.  

I have a Cruccial 1Gb module in each of slots 1 and 2, and two of the original 512Mb modules in slots 3 and 4 .

However, in  the memory information given in BIOS, only the modules in slots 1 and 2 are showing up.

Is this because the 1Gb DIMMs "overpower" the 512Mbs, so to speak, and render them null and void?   Or should I still get 3Gb of working memory with this setup?    

Ram is Paired and its NOT  1 2 3 4  so your mis matched pairs think you have 4 x 512 = 2 gig.

The Ears of the Ejectors are colored differently to show you the Pairs are 1 3 White Clips  then 2 4 Black clips.

Thanks - however, by "paired" I meant inserted the two 1Gb modules  in slots 1 and 3 and the two 512Mb in slots 2 and 4.  

BIOS shows 1 and 3 as containing the 1GB modules, but 2 and 4 as empty.