Ram Upgrading Question

[Spiders]

When upgrading RAM what are the rules on speed and size?
I currentrun this, 4 slots, with dual channel support. I want to have more RAM I currently set up like this

(slot one) Blue: 1gb ddr2 667
(slot two) Black: empty
(slot three) Blue: 1gb ddr2 667
(slot four) Black: empty

my question is if i want to upgrade, do I have to use the same as what I have?
meaning do I have to upgrade to 4gbs? or can i just fill one slot with like

1gb ddr2 800, or 667? do the speeds have to be the same? all system specs are on bar

 

[strategic]

If you wish, you only need to put in 1 memory module.
It should be the ame as the ones you have, if it is faster, it will only be as fast as the ram you currently have, if it is slower, you rcurrent ram will slow down.

 

[Tedster]

read: https://www.techspot.com/vb/topic65114.html

 

[Spiders]

So could i just put one stick of 512mb ddr2 667 ram in one slot and it will work? I'm not looking for a huge upgrade for RAM just enough to cancel out the RAM the OS and other background programs use, I have 2gigs but only have 1600 avaliable, with 512 more I would have at least 2

 

[strategic]

Sure you can, my PC had 1-512MB stick in it with 1 empty slot (something you don't see too often from a manufacturer). I just popped in a 1GB stick in just yesterday and it works great...