Hey,
I don't know if this is the right place to write here, but anyways, I'll write.

I didn't have any problems before format setting games to higher (above normal/high priority) and the games did run better than normally, everything was fine, but now after format, when I set for example medal of honor or soldier of fortune or any other game to higher priority, it works also, but some problems, like for example my mouse buttons doesn't work, sometimes it works, sometimes no, sometimes with delay (shooting in this case because of shooting games) and I have no clue what to do

any help?

Maybe you are missing some Windows Updates since you just formatted.

However, it is best to set it to Normal priority to avoid the issues you have already experienced. If you are setting a game to higher priority than the system processes then you are risking the stability of the system.

If you are overclocking as well then that could be another cause of the problem.

I just read into your situation and apparently 'Above Normal' priority is more stable and should work better than 'High' priority.

The problem with 'High' priority is that some system processes are not able to work as fast as they should or at all eg your mouse etc.