Dell 5150 - memory issues

Horlock

I've just bought a new Dell 5150 which came with 512MB ram (2 256MB sticks) and it has 2 vacant slots left. I have lying on my shelf 2 sticks of memory a 256mb PC3200 DDR ram and a 512mb PC3200 DDR ram.
The question is can I add them? Can I do any harm? Will it definately make an improvement or will it make things slower?
I don't know the modern stuff about ram - I've heard mention of DDR2 and to be honest I haven't got a clue what it is or whether the new computer uses it - I tried going to crucial website to see what ram they recommend I buy - but the form asked questions I don't know the answer to.
Any opinions. The memory in the dell is not labelled but the pdf I received states "512MB Dual Channel DDR2 400MHz (2x256) Memory".
Any help greatfully received.

IvanOpinion

I'll be honest by first saying memory is not my forte but I think they may have to be added in matched pairs therefore a 256 & 512 would not work together .. open to be corrected on this though

Ivan

fairytooth

These are DDR2 DIMMS (not SIMMS) and they do not need to be matched pairs but they DO need to be DDR2 - they are not backwards compatible with DDR.

You should be able to follow the Crucial wizard or just ring them to be sure of the right chips if you want more RAM..