I'm looking to maximize my computer's gaming performance, without buying a new machine - I would like to know what the weakest point of my machine is so that I can get the most logical upgrade to boost performance. I have 2 gb of Ram, a Radeon X1650 series graphics card, and an Acer Em61sm/Em61pm motherboard.

the product description in your post's header doesn't match what you describe in the body of your post. you also didn't mention your CPU at all in the body of the post. once we know what you have, people can make suggestions for hardware upgrades. keep in mind that if your hardware is too old, the common suggestion will be to save your money for a whole new build, instead of dropping cash trying to keep a dinosaur up and running.

The header is wrong, it's not an ED422a, it's an ED423a. And I strongly doubt my pc is a dinosaur, it hasn'T been three years I use it, and I can run games like Mass Effect and Fallout 3, just, not with very high graphics capabilities - the computer seems to be needing extra ram, and a better graphics card. I have a few, more specific questions though, if I buy a ram upgrade... a) is it true that if I want to upgrade to 4 gbs of ram I have to buy all of it new, and take out my current ram, or can I mix and match/find a ram stick of the same model that I currently use? b) Secondly, using a 32 bit vista processor, is it logical for me to upgrade my Radeon X1650 256 mb, 333mhz to something like a EVGA 9800 GTX+ 512mb - Is it worth the upgrade, will my computer take good advantage of it, and can my computer run it?

no, you don't need to worry too much about matching RAM exactly, just so long as DDR2. Ideally you want them to run at the same frequency (400mhz, 533, 800, etc), but you can usually adjust this in the bios. as for the graphics card, that would almost definitely be worth the upgrade. the 2 things you want to pay attention to are slot type (PCI express), and Power Supply Requirements - make sure your PSU can handle the new card.

Thank you for your quick answers, UpAndComing. How can I find out the frequency of my current RAM and find out what my Power Supply is? The current slot is a PCIe x16 so that's compatible, as for the power supply I'm unsure how to define it. Oh btw my cpu is a dual core AMD Athlon 64 X2 processor, 2.4 Ghz I believe