Toyne,
Nice box.
But the first thing you really need to do is open that box and get the computer outa there - it's yearning to breathe free.
I didn't catch the motherboard, processor type, processor speed and Microsoft OS - could you help me out?
DDR 1000 MB DDR seems to be a sweet spot, depending on your budget and what you want to do. This
thread may be useful. I would go 1000 MB if budget allows - and I'm a cheap date.
Some DDR performs better in matched pairs - others, it does not matter. Depends on the motherboard and such. That is where your computer manufacturer's tech support earns it's keep. Determine what DDR you have first - brand/speed, etc. - look on the DDR chip itself and copy down brands and numbers - before buying more. Here are some
guides if you wanna really dig into it.
Two separate sticks of RAM (instead of one larger stick) can make a real speed difference on some boards with on-board video sharing motherboard RAM.
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Video cards:
It depends on what you are gonna be lookin' at.
2D? I.e., staring at print / typical schoolwork / office apps all day - go Matrox. You will be glad you did.
3D gaming? It may depend on your game and your budget.
Then again, if this has an integrated monitor, I'm not at all sure that you can use a separate video card, anyway.
Monitor integrated or separate?
And I do not see an AGP slot in the specs you quoted - without one, your video card choices may be a little limited.
This may be more of an internet/word-processing machine than a graphics/gaming workhorse.
If you know what video card you want, try the same places you are shopping for DDR.
If you are not sure, get back to us and we can all be unsure together.
Happy computing,
Epaminondas