Weird image file format...

seems to be a medium resolution image file from dages elite. not sure what that is; just googled it.
if you have a windows pc, you might try irfanview--that opens pretty much anything...

 

It's an Atari graphic file format of the app degas.

According to http://lemkesoft.com/en/gcabout_formats.htm, GraphicConverter X should be able to open and convert these files.

 

Yes. If those are Atari files--and it seems that they are--then they are also very old--very, very old, in fact. It is easy to imagine how all 100 files may have been corrupted over the decades.

 

If it exists, GC will pretty much open it, but I'd have made the same assumption as you about the corrupt files.

However, based on the age (especially if it's a CDR), it is possible... so have you tried copying one of the files off the disc onto your hard drive and opening it from there? That will usually tell you wether it's damaged or not, though it's not fullproof.