The Intel technical department does not support modded drivers at all. Intel recommends downloading customized drivers from your computer manufacturer or generic drivers from the Intel web site.
Thanks for answering. If I did know I wouldn't use drivers of course. Now I'm not sure what is wrong. I checked graphic card in Windows XP- no problem at all. In this case I think something was messed up with system, not HW and maybe GPU's MHz is correct.
If I would like to reinstall drivers for Windows 7 , from scratch I mean, what should be done? I reinstalled them few times but with no success.