What kind of old games do you want to use shaders with? As long as they are hardware accelerated 3D (Direct3D or OpenGL), you can use tools to force the video card to load a shader whenever an application is launched. An example of this kind of tool is ATI Tools.
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But there is someone who remembers you
Someone waiting for a sign that leads the way to you
There is someone who will die for you
Keep that in mind when the hope fails