This question seems to get asked every day. As said above, you need a new video card to play whatever game you want to play. At this rate we're going to need a stickied thread on this forum that tells people they can't download any version of Pixel Shader.
Yeah, I see this question asked almost every other day.
As mentioned, Pixel Shader 2.0, 3.0, 4.0, and 5.0 are not software downloads. They are specific hardware that is part of the video card. Therefore, you need to buy a new video card for whatever game you want to play.