Thanks guys for response. I have a lot of bad block in event viewer and whenever bad block occur my computer go in short freeze. Also, this is 5-year old hd, so I think it going to die. I done chkdsk /f and it did not help. So I already bought new hd, WDC WD5000AAKS and I'm moving my data on it. After that I'll not use old disk at all. Also, I recently replaced my computer with new one because of dead motherboard and I kept my two working HD-s, but one which is now getting this bad blocks behaved strangely, for example manufacturer utility does not recognize it, Acronics backup program does not recognize it, tool Drive Space Indicator won't show indicator on it... Cheers