Thank you,

it helped to get rid of selection tool distortion.
but still borders of the selection tool "blinks" when I move it.
is it normal ?
(it looks like a kind of screen refreshing problem now)
(I'm going to check the settings for that)

and after disabling the Aero feture, I have realised that when I minimize or maximize any window, window movement is a little bit "chunky" now.

maybe this Aero addition was made for this aesthetic resons.
but I don't care that. I only want to use my new software.

Hopefully I have never had this problem before, especially while I was using 3ds Max and Unreal III Level Editor where my major projects are held in.

thanks for your help.