Windows Media Player won't play movies- only getting sound, can anyone help me?

Basically, it's like this- I put in a DVD into my computer, and I go to Windows Media Player to play the movie get to the menu it gives you if you have a movie in the computer, like how it shows the movie's chapters in the Library. However, I only get the sound that comes with the movie- I can't watch the actual movie itself. Basically, if I click the chapters, I don't get the movie. If I click 'Now Playing', I just get a picture of a music symbol. Does anyone know what's wrong- this has always been my way of seeing movies on my computer and I don't know what else to do and I have no idea how to fix it! I use an Acer Windows 7 64 Bit deluxe if that is important, and Acer Arcade Deluxe PlayMovie still works for movies, but in the long run, it really is inferior to Windows Media Player. I've tried a system restore, but it doesn't work- mostly because I can't go very far with system restores on this computer. Can anyone give me advice on how to do this? ALSO, while I honestly don't remember the way to get to it, I have done this- basically I went to a check box, and I clicked the one by Windows Media Player- it said this had uninstalled it and the computer then restart. I went back and checked it again so it would reinstall- no luck. This also sometimes affects my internet- on the "Using Windows Media Player 12 for Windows 7" page on the Windows website, when trying to watch the Burn a CD video, I get the sound, but all I see for a video is basically lines, like when it gets louder the wavelength increases. What can I do to fix this?

Give Video Lan Client a shot, as it does the same basic thing as WMP.
Maybe even realplayer for the rest of your media, VLC for DVD's and real for everything else.

It probably has something to do with your codecs (or to be more precise; the fact you do not have those) Original DVD movies use MPEG2 decoder.
You should either try to get and install this decoder or use a different player what allready has the codec like WinDVD or whatever.

Here is a site where you can get codecs.

Free-Codecs.com :: Download latest audio codecs, video codecs, codec packs and tools, FREE!

Under the "Featured" column there are some codec packs. I've done well with the "Klite Codec Pack"

I don't recommend codec packs, as they can make problems with other applications. Open the disk and try playing the files directly from the VOB folder. If they play ok, it's just an issue with WMP and the way the disk was authorized. Like mentioned, go with better players like VLC, KMplayer etc.