DVDs won't play, please help

Something is acting up on my computer. I tried playing a DVD with PowerDVD 6.0 and also wmplayer, but it doesn’t work. In PowerDVD, I can see the video only when I right click, then I can see through the black text to see the motion picture. In wmplayer, I get a gray screen that I cannot double-click to full screen, rather I have to Alt-Enter. Can anyone help?