Everytime I turn on my computer, before the login screen, the message "Checking File System on C : the type of file is NTFS, One of your disk needs to be checked for consistency." show up with a black background. what is that, it was never happens before. And the computer is really slow these days, and sometime it freezes. When i open the disk defrag box, and i cant see the C, only recovery can be defrag Sounds like its the issue of the hard drive, my computer used to running very fast. Can someone help me fix this problem?