You know, recently I released a 2 disk DVD set for sale about Emulsion Making and Coating.
Now, this is not a sales pitch it is a story about making the DVDs.
First, the software for the camera is incompatible with most editing software so you can't see the image or hear the sound (take your pick). You have to get special translating software to yield 2 files of image and sound and then these go into the editor. (this is true of many editors).
Well, once edited, you make your master and take it to a shop to dupe it. They read it! Hah, the errors climb during reading and their software tells you it is either a checksum error or one of 2 other types. If the number of errors climb over a certain amount, the disc cannot be copied.
The engineers at the shop told me that most common DVD writers made disks with so many errors in dupes that their shop (and other) were unable to copy them. I had to make 3 masters before I got one that had a low enough error rate that dupes could be made. Their software was able to fix these errors but this indicated to me how chancy this process is.
Almost all disks have errors or create them and only smart algorithms will fix the problem.
At the present time, I have many PDF files that will not open. They are ok, but the Adobe reader has changed so much that older files cannot be read. I have Word files that com from the previous version that I am using that I cannot read. I get very esoteric error messages that when searched for on Google indicate a "protection" error based on upgrades to internal Word and Office security which has rendered the files unreadable by the new version.
Interestingly, if I install the current Word on the old computer that the DOC file came from, it can be opened just fine due to the lower security OS (ME vs XP).
The point of this? Computer files seem to become obsolete or contain many errors which makes it difficult to work with them over a time base that is probably on the order of 5 - 10 years.