What's up with my backup disc?

Hmph!
I have a DVD from 2004 where i put files i used to create a playable disc.
A friend asked if i could retrieve some .jpgs
I can see all the files in Explorer when i put the disc in the drive, but if i try to copy any of the .jpgs off to my local hard drive, it give a 'Can't Read From Source File or Disc' fail message.

when i put the backup disc into a mac i can see the folder but no contents.

any ideas?
thanks in advance

Update: at one point, the error message changed to Error Code 0x80004004. So i ran sfc /scnnow as per instructed. it said that something was repaired.
Now, when i try to preview one of the jpgs, i can see approx the  top 160 lines of a 480 x 720 image. The rest is grey.

i have no idea if that is an improvement....