Upgrading Pre-Built System

[Guest]

Ok, so currently my system is
Intel Core 2 Quad @ 2.4 Ghz
2 Gig DDR2 Ram ( 1 gig x 2, dual memory )
Mobo
Intel G31/33 GMA 3100
E-Teck 350 Watt PSU
Vista Home Premium 32 bit
This is a HP system, so OCing the CPU is out of the question

Now, IMO the CPU is good enough, but the ram is a little low, so I am planning on upgrading that to either 3 gig or 4 gig of ram, but do I have to install the memory in pairs (512x2 or 1x2) or can I just install a 1 gig or 2 gig ram stick. I am not interested in getting dual channel because it is not that helpful, my main question is weather or not I have to install the memory in pairs or can I just install an additional 2 gig stick with the same speed with my current setup so it would be 1 Gig, 1 Gig and 2 Gig equaling 4gig of ram.

Next my fail graphics card: I do a gaming, from light to casual but I can not even play games like combat arms smoothly with that fail chip. I also watch HD movies and do a bit of editing. So far I am looking at these 2 cards 1: 4350 and 2: 4550. Which of these would be better, and what other cards would you recommend for the same price range.

And if I need to I can upgrade the PSU too, but would it be necessary? PSU: I was looking at this because it is plenty powerful enough and it guranteed to give me 400watts+ even though it says 500watts and also has enough connectors and is 120mm fan, which is a plus for me.

 

[Pyroflea]

You are able to install either a single stick, or a pair of sticks. A single stick will bring the original two out of dual-channel mode into single-channel mode; installing a pair will not. However, being only 32-bit, Windows will not recognize 4GB or more.

As for graphics card, you need to be sure that your motherboard even has a PCI-e x16 slot (which it should[I hope]). If it does, then you're able to install a graphics card. I'd opt for a bit better card like this:
http://www.newegg.ca/Product/Product.aspx?Item=N82E16814161297&cm_re=ati_4850-_-14-161-297-_-Product
But that's just me. If you do go with one of those cards, go with the 4550.

I would recommend upgrading the PSU personally, just as OEM's like to throw in cheap-o PSU's. A PSU is not something you want to skimp on; it's failure can potentially cause damage to your hardware. Something as small as a 400w PSU would be plenty; the Corsair 400CX (or w/e it's called) is a nice unit; I'm running one in my home server.