cool I have 2.5 gb. I wonder if it would be faster if I just used the 2 gig stick without the 512 one, I wonder if that would make it faster?(because it is all on one stick?)

It doesn't make a difference if it's two or one. But remember that all the RAM runs at the speed of the slowest DIMM. So if the 512 is rated slower than the 2 gig, then yes, it's slowing you down. If not, then it can only help.

then whats the difference with dual channel memory?

What do you mean what's the difference with dual channel memory?

well isn't it faster, like each stick of memory works together?

3 gigs ram. amd phenom quad core processor 2 gighertz

No. Each dimm will operate at the speed of the slowest one installed.

this is why they say when you buy ram to buy two of the same or buy one that matches and existing one in a dimm slot...

example 512 stick and 1 gig stick is a no no your 1 gig stick will only run 512 cause the other is 512 so ur only getting 1 gig of ram...

but if you buy 2 1gig sticks and replace the 512 u'll have 2 gig of ram.

Well, no. That's not true. You get the amount that you install. If you install 1 Gig and a 512 meg, you get 1.5 gigs. But it's the SPEED at which they operate. Speed is different than capacity. It's good to have matching sticks, but they don't need to be the same size.

by speed do you mean bus? if so then i see what your saying. i thought what i said above was wrong... but wasn't sure haha.