Are you certain that the drive in your pc is a dvd drive? If it is just a cd drive, it won't be able to see material on a dvd.
Assuming it is a dvd drive, if this video was playable on your dvr, it is most likely in dvd-video format. If you are using XP as your operating system, it doesn't recognize dvd video natively. You must use third party software for that. I suggest getting a free player called VLC. www.videolan.org
If VLC cannot find and play the files, try the free edition of ISOBuster. It should be able to find the files on the disk and allow you to transfer them to the hard drive. You can find ISOBuster here: http://www.isobuster.com/
Post again if neither of these help.
Someone more familiar with Macs may answer here with more suggestions.