I have ATI Radeon X550 Video Card and it support truform, and have a ATI Radeon HD 2600 XT.

And have a question: does anyone know how to emulate truform?
These very painful to have modern computer and always change video card i think newest video cards can able to ate trufrom without loss of speed.

does anyone know how to emulate truform?

TruForm was a marketing term used by ATI for an early attempt at hardware tesselation.
These days the better general approach would be to use Tesselation Shaders (although your 2600 XT won’t support OpenGL 4.0) or to some limited extent Geometry Shaders.
There also exists the possibility of using CUDA to perform the task instead:
CUDA paper

ATI did release an extention for PN Triangles (TruForm)

Here are your options to do tessellation:

ATI_pn_triangles (on pre-ATI HD2000) -> “TruForm” tessellation
AMD_vertex_shader_tessellator (ATI HD2000-HD4000) -> programmable tessellation with fixed tessellation factors
ARB_tessellation_shader (ATI HD5000+, NVIDIA GF400+) -> fully programmable tessellation

(While geometry shader could be used for tessellation, I would not recommend it as it would have terrible performance, especially on NVIDIA GPUs)