Why My DVD ROM behave Mysteriously??

Well I have a DVD drive which is capable of writing. Its model is Samsung 16X. DVD drive and Writer. It sometimes does not open when I pressed the eject button or when I command it to eject from the system. And more over, sometimes it can't read the DVD, though I give it almost a new DVD to play. It only makes sounds but does not show anything in the screen. And another thing, sometimes it can read DVD but can't copy the files in the DVD.
I want to know what is the probable cause of these problems. Why does this occur? Is the DVD drive gone? or is it something else?
Is there any way to fix it? Or should I buy a new DVD drive for my PC??
Please explain those problems so I can take a proper decision to replace or fix my DVD drive.
I need a quick answer. Please respond as soon as possible.
