My PC has become very slow for unknown reasons. At times my CD drive cannot read (i dont think there is anything wrong with my CD drive or my CDs). I have windows XP service pack 2. I restored my system to a previous date after which my CD drive was working fine but still my PC was slow. I ran a virus check which was negative. I then tried to run scandisc on drive C where i was told that it can only run during start up. So i restarted my PC where i got the message "could not open drive for direct access" with that scan disc stopped and windows started. I then tried to defragment c drive but was told that it can only run after the scheduled scandisc takes place, which by the way refuses to happen. then i tried to restart my PC in safe mode. But my pc hanged when it reached a black screen with lots of characters. So i had to reboot in normal mode and my PC continues giving sluggish performance. and all the abovementioned problems keep recurring and i am forced to restore my PC over and over again.