A bundle of relevant information here, thanks to many, but specifically
BigChickenJim.
Given that you're looking for other opinions, I decided to chip in.
You are running a
32 bit version of Windows 7, which means that you would need to acquire a
64 bit version in order to validate adding more RAM, given that the former version only addresses up to 4 GB. Because the GPU's VideoRAM and other devices' Input/Output are memory-mapped into system RAM, bearing in mind you have a GPU with 1 GB of VRAM, you end up with barely over 2 GB of usable RAM. This is somewhat problematic as far as recent games go, although the recommended settings for the ones you brought up, appear to be around the aforementioned amount.
Nevertheless, this likely is one of your issues (run Task Manager on the background while playing any of the games for a couple of minutes and then check the graph to determine the amount of available memory in the meantime and diagnose this as a limitation or not) and as pointed out, not only would you need to add extra RAM, DDR2 no less, which happens to be more expensive and slower than DDR3, you would also be required to install the 64 bit version of the OS, for it to take advantage of the extra physical memory and allow the 32 bit games to make full use of the up to 2 GB they're entitled to.
If this proves to be one of the issues, which frankly, it will ultimately come to be as you approach more recent gaming titles.
Moving on to the GPU - the resolution you're aiming at may demand more than what it can deliver. Again, the games you bring up aren't particularly exigent, but later on the road you will likely notice the absence of rendering power. Utilizing a similar method to that described above with Task Manager, you can leave GPU-Z running on the background whilst you game for a couple of minutes and eventually browse the data on the
Sensors tab, in order to acquaint yourself with the usage percentage of the GPU. Additionally, if you tick the
Log to File option, GPU-Z will write down the information for you, for posterior analysis. Make sure you un-tick the option once you're done recording, not to end up with an immense and unneeded log file.
Where the CPU is concerned - this bears yet again the mention of the fact that those games aren't Quad-Core demanding, but it certainly wouldn't hurt to have the extra machinery - you're running a somewhat obsolete gaming CPU. Again, Task Manager to the rescue and to provide some information, regarding CPU usage.
So far, I've attempted to provide easy diagnostic methods, for you to acquaint yourself with the response of your hardware to the software demands. Discarding for a moment the upgrading venue, you would want to attempt over-clocking the CPU and GPU - depending on what's being strained the most. CPU wise however, given that we're talking about an OEM board, you likely won't be able to follow this route, which only leaves GPU over-clocking. From what I can tell, this won't solve your issues, but let's explore that option for a minute and hopefully you can report back with relevant information that will allow us to definitively deem your whole system as obsolete and from there on, I'm sure
BigChickenJim will be happy to help you with both of his *rubbing hands*.
I would generate a few, 3 or 4 results per each game you're having issues with, to determine whether over-clocking the GPU is a relevant course. If you come to the conclusion, after analysing the GPU-Z generated logs, that its usage is constantly above 90-95%, then over-clocking will help.
Firstly, however, I suggest you download
AMD's clean-up utility, run it, reboot and proceed to install the the latest stable release of Catalyst Software Suite (13.4 as of today), which you can download from
here.
Do not install Catalyst Control Center - un-tick it during the installation and instead, download
MSI Afterburner and set it up so it starts with Windows, as it's much lighter on resources and will likely suffice your needs. All this procedure should hopefully prove a solution to any driver issues.
From there on, if you happen to identify the GPU as the culprit, you should be able to tweak its clocks via MSI Afterburner, using the sliders - they should be set to 850/1200 by default. For guidance on HD 5770 over-clocking values, consult posts around the web, or if it comes to that, I'll provide you with some.
I wouldn't get my hopes high, not unless this issue suddenly began occurring on previously smoothly-running games, which you weren't clear about, in which case software could be the culprit, best case scenario. Given that you would indeed need a complete system upgrade, do explore every possible course until you've definitely ruled out every non-upgrade related fix.
JD