I want to burn movies, but once i put in my DVD cd, which is the one i have used before, and it did work perfectly... but now its tellin me it cant recognize the disk... please help!!

You need to check several things, firstly, is the bois reporting it correctly. Secondly, is the power connector properly seated in the back of the burner. Thirdly, is the data cable seated correctly. And finally, is the jumper on the back of it set correctly.