Geforce 9500 GT : CUDA not working ?

With Geforce 9500 GT and latest 341.44 windows 7 64bit drivers, same Freemake Video Converter same with Xilisoft video converter, CUDA is not used and the relative option is not possible to check.
Also tried to install Nvidia CUDA 7.0 but the software says me that I have no compatibile graphics hardware.
How to solve ?

I think Geforce 9500 GT is a compute capability 1.0 or 1.1 part. GPUs with a compute capability < 2.0 are no longer supported by the latest NVIDIA software, neither for CUDA nor for graphics. You would have to use an older version of CUDA and an older version of the drivers with this GPU, but I cannot tell you which versions specifically you need to install. Maybe someone else here knows for sure.

You may also want to consider upgrading to a newer GPU, even a modern low-end device is likely still faster than the Geforce 9500 GT.

I believe 9500 GT is a cc 1.1 device:

and cc 1.1 devices should be usable with a r340 driver which includes the 341.44 driver listed.

CUDA 7 is indeed not usable with this GPU. CUDA 6.5 should be usable.

Having said that, it’s not clear to me why those applications would not offer CUDA acceleration with 9500 GT and 341.44 driver. I’m not sure this is the best place to ask such questions. The developers of those applications would know what requirements need to be met (and may indeed have published those) in order to enable the CUDA acceleration option within those apps. In fact, xilisoft has published a page indicating 9500GT is supported:

My guess would be that the real dependency here is on NVCUVID/NVCUVENC, and the associated libraries. NVCUVENC was deprecated prior to r340 I believe, and I suspect that r340 does not include the NVCUVENC dlls.

If there is a previous r331 driver available for this GPU, I would suggest trying to use that if the desire is to run these video conversion engines.

And if you want to use such a driver, then you will be limited to CUDA 6.0, if you also want to use the CUDA toolkit. (Installing the CUDA toolkit is probably not necessary for these video conversion engines. The nvcuvenc library dlls should be installed by the driver.)

This 332.21 driver might be a good choice:

But what is the most economic graphic card that runs in pci-express with latest cuda in windows 7 64bit ?

What is “economic” depends on your circumstances. You should be able to pick up a GTX 750 with 1 GB of DDR5 memory for about $120 if you are in the US. That is a card with a Maxwell-class GPU.

If I have several MKV h.265 to convert in h.264 is better on old pc with a good recent graphic card of is there something external like nas that make the conversion for me in same or better speed ?
What model of nas or “conversion machine” ?