HI to all.... I have a Big Problem in my System.. It is showing C Drive is Full But I didn't Install any?

The fact that Defrag isn't working due to disk errors could be a cause. Also, there is a type of virus called a rootkit that replicates itself until the drive it's on is full. Go to a href="http://www.download.com" rel="nofollow"http://www.download.com/a and download these three applications: AVG 8.5 Free, Spybot Search & Destroy, and Adaware AE. All three are free and very good at cleaning and protecting your hardware and OS. With Spybot, I would not recommend you install the Tea Timer unless you're somewhat familiar with Registry values. (The Tea Timer alerts you whenever something attempts to modify the system registry, and it'll ask you to allow or deny the change.) Spybot also has an Immunize feature that blacklists known bad websites, add-ons, and settings that can compromise your security and privacy.