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?

Possibly something in your software configuration changed, so system needs more resources, when you set games priority too high, system itself gets less then needed resources and then you get problems with response from devices etc.
Check if now, after format you have more software running or if system itself uses more RAM/cpu while idle then it did before.