I recently purchased games on steam for no reason(maybe cause they were on sale; GTA: IV, Medal Of Honor, NFS: HP 2010) because the only game I play all the time is counter strike 1.6 and counter strike: source. Well, they all lag, a lot! I dont have an expensive gaming computer because I didn't think I needed it. So any ideas on what I can buy/upgrade to play these games with decent graphics and no lag? (:
Looking at your link the computer isn't that bad. You have a quad core AMD CPU, and a free/open PCIe 16x slot. So assuming your PSU is up to it you can put a real GPU in there and stop using that onboard 4200. You should be able to put the 5670 in there no problem. Considering how expensive it is and how much more you can get for just a few $$$ more, I'd open the case to see what PSU you have. You need to figure out how many amps on are the 12V rail. Look at the PSU and look at the chart on its side. If it has more then one rail, see if there is anything like "12v1 and 12v2 not to exceed xxxW" written anywhere.
Brand and Amps matters more then Watts. Good brands are Antec, Corsair, Enermax, and Seasonic. How many Amps depends on what parts you have, or will have. Any 30A PSU from those I listed previously will handle most cards ok. Dual GPU cards and the highest performing cards will be a problem. If your looking at mainstream GPUs like the 5770, 6850, etc then your fine with a 500W or 30A PSU. If you want to CF them or run a 6970 or 5870 then you might need a bit more.
Not a bad PSU, but its an odd one. More then enough power for a single card, but not enough power to run two big ones. And if you are going to CF two 5750s, your better off just buying he bigger card which it can power. See about getting the EA500, or if you want to CF/SLI two cards later the 750.
Edit: forgot the ram question. Can you even buy 512MB cards? Assuming you are dealing with any normal res (1680x1050 or higher) you'll want 1GB.
ok if you're a newb at this you may want to ask your friend to assemble the psu since it can get a bit tedious. you should watch him by the way since it's very fun to do it and you should learn a thing or two and perhaps build your own someday
anyway, i think i'll give you specific items and i think this is the BEST items for your budget (you could find better deals, but at least find the same model for the video card and ~wattage for the psu)