dvd decoding

[jlb]

Hi, Like to say hello being a newby to this forum. I am in need of a bit of help with my pc. It's a Dell running vista. I re-installed the software using the dell reinstallation dvd as it had lost a few files due to me uninstalling a couple of programmes.
The problem is I can't get the dvd player to work properly--when I try to watch a dvd on it the picture is scrambled.
Any help would be greatly appreciated.

Kind regards,
John