Old computer files

What do you do about old computer files?
 My husband said - in the 1990s - why do you print everything out? It's on your computer so save it on your computer. 
Well, now I've lost a lot of stuff that I 'saved' on the computer because digitalization keeps changing format. Recipes are gone. (unreadable files) Manuscripts that I didn't print out are gone. 
I'm now going through my (new) computer and testing each file and deleting things that I no longer can open. I did print out everything from college, so now I'm trying to find that stuff on the computer and delete it. (also so much college email I need to delete, because I did print out the important stuff. 
When I moved from the east coast to the west coast, I looked at all the 5 inch and 3 inch floppy computer disks that I had saved, shook my head, and tossed them.