My system is:
operating system: Windows 7 Home Premium 64-bit (6.1, Build 7600)
Processor: Intel(R) Core(TM) 2 Quad CPU 8300 @ 2.50GHz (4CPUs), ~2.5GHz
Memory: 6144MB RAM
DirectX Version: DirectX 11
Graphic card:
NVIDIA GeForce GT 220
Approx. Total Memory 3802MB
Current Display Mode: 1920 x 1080 (32 bit) (60Hz)

This is quite a new computer which was bought April-May last year and I'm running Witcher 2 on Minimal Details, I've turned everything off, antyalising etc. and the game is still lagging, could you tell me what I've got to change/do so the game runs properly without lagging? when I clicked automatic setup (or something like that ) it puts everything on high details and the game lags like hell, Please reply quickly because I really want to get on with this game :)

Your graphics card is equivalent to something like GeForce 7800, pretty much meaning that it's completely outdated for anything but desktop usage. At the very least drop the resolution lower.

Don't take this the wrong way, but a GT 220 is a pretty anemic video card, and I suspect why you are having issues, though the first thing you should do is make sure you don't have the Nvidia 3D drivers installed.

The minimum spec is 8800GT which is about 2-3 times faster than GT220. So yeah, you should replace the video card with something beefier (like GTX 560 for example). Everything else seems perfectly capable of running Witcher.

He may want to check his power unit. Pre-build computers tend to skimp there, and many people who buy a pre-built PC will find they need to upgrade that in order to put in a real gaming video card.

I'm running the Witcher 2 on minimal settings with resolution 1280X960 on my 4 year old laptop with 2x GeForce 8700GT in SLI mode. Technically it's below required but it's playable (~20 fps in intense parts) and it looks pretty good for me despite low settings. So, lower the resolution to some proportional values. And I run the GOG version with no DRM (people here mentioned that DRM eats ~10 fps).

Not quite: I have a 7800 GS, and a GT 220 is much better. The 7800 GS can only manage 3 to 5 fps at 1280x720, and I'm surprised it can do that.

The GT 220 sits between the 9500 GT and 9600 GSO in performance, which is to say it's not adequate to run the game at full resolution. Maerd's experience with his 8700 GT's is closer to what you should expect.

With reduced resolution and low to medium settings, you might get away with it. And revial's comment is spot on: a system that came with a GT 220 probably came with a minimum-spec power supply, and you would have to upgrade the power supply as well.

With a weak quad core like a Q8300, I wouldn't go overboard with the GPU either; something like a GTX 560 would just transfer the bottleneck to the CPU.

so would that GTX 560 solve the problem?

Well, it would at least determine how narrow a bottleneck that Q8300 could be.

Expensive way to find out that an HD 5770 or GTS 450 would work about as well, I think. I wouldn't use a GTX 460 or 560 with less than a Core i5 or Phenom II quad.

I'm pretty sure that CPU would be bottlenecking even say...a GTX 260. Just saying.

I agree, but there's a point of diminishing returns when you go shopping downmarket for GPUs. The 5770 and GTS 450 are $110 to $120 (US), and anything significantly less is significantly worse.

I'd bet a fair amount of money on it. i doubt it's your CPU. People who game love to talk like you need a bad ass CPU for shit, but it's bogus for 92% of games and I haven't seen evidence that a 2 GHz quad core won't be up to this task.

People are right about the power supply issue though. There's a sticker on your PSU that says how many watts it provides and how many "rails" it has. You need at least 18 amps on a 12V rail to run a good video card, and you need about 450W total system power. (And don't believe the people who tell you you need more than that. If your power supply legitimately produces 450W, you're well in the threshold needed for a gaming machine unless you have a SLI/CF setup.)

That is not good advice, and your statement that anybody who disagrees should not be believed is offensive.

A system configured with a high-end modern GPU is going to demand approx. 34 amps combined from the 12V rails. And you can't add the rails, either: the power supply must specify a combined power or combined current at 12V. (Example: if a PSU is specified for 408W combined at 12V, that's 34A.)

There aren't any sub-500W power supplies that can deliver that much current, and there are few well-made sub-500W supplies, not even from Corsair.

500W is the practical starting point for a power supply to support a modern GPU. And it should have dual 6-pin, or better yet, a 6+2-pin and a 6-pin PCI-e power connectors.

Start by looking at total system loads over here: http://www.anandtech.com/bench/GPU11/229

Could you please find me a single benchmark on a modern system that shows total system load for a single card machine in excess of 450W? 34 amps on a 12V rail is 408W--that's on one rail! Total system load is not just on the 12V rail. I should have been more specific: you need a separate 12V rail for your card only. 2 rails PSUs are readily available.

Don't believe the PSU hype.

For starters, never, ever figure on running a power supply above about 2/3 rated load. Even if it is warranted to run at full rated load and operating temperature (and if you read their specsmanship carefully, very few sub-500W power supplies are so rated: even Corsair's are not rated for operating temperature above room temperature), you will get neither good regulation nor good efficiency. Bad regulation will cause hard-to-repeat errors throughout your system. Lots of systems that are reported as being unstable are unstable because they operate the power supply in a range where it no longer regulates well.

My Q9550 and 3870 rig alone can pull 360W (don't make claims based on playing a game; make your claims based on something really CPU and GPU intensive like running both a CPU and a GPU instance of Folding@Home), so no way am I running that on a 450W supply. So I do not for an instant believe the claims in the article.

And you cannot dedicate a rail to the GPU, because the high-power two-auxiliary-socket GPUs are designed to require supply from two rails, and because no single rail in a multi-rail design can supply the peak current requirement.

Do better homework than that if you want to come in here arguing that people can get away with cheap power supplies.