Can't read data from DVD?

I can't get my DVD drive to read the DVD. It has some old files on it. When I click on properties it says total size 4.37 GB, free space 308 MB. I've tried double clicking it, right clicking and hitting explore. I went into the properties/tools/disc check and it said 'Could not be performed because windows cannot access the disc.

I'm using Vista, any help?
Thanks