I have seen multiple posts about this problem and it took me a while to find the root cause. For me, moving files to another hard drive, disabling the Windows indexing or setting the folder options to general did nothing. In my case the problem was ADAWARE antivirus. Once I removed it, my performance returned to normal.
Damn! that's it! you rescue another person! thanks alot! Once I turn off the real time protect, play video instantly!