I helped me friend find out the problem of delay that is without reason. Finnally discover that the CPU's temperature is too high (~65 degree) to be stable working. Then open the case for suffering to the surrounding temperature (~25 degree) and the system will become more stable about less than 60 degree. So I have been taught a lesson that it does not always need to reinstall your PC when it seems to be in the mess and check the temp. of your pc at first.
It's my humble opinion, and hope it could help, thanks!!