I am at my mum's for Easter and one of the first things she asked me to look at had to do with her computer. She had this document that she wrote using Microsoft Works aeons ago that she wanted to open again. Of course, she's now using Microsoft Word and Word has no idea how to open Works files, even though both products are produced from the same software company.
What to do? The answer is very simple but rather counter-intuitive for people not used to open source software: LibreOffice. From the point of view of someone who lives in a world where closed source is the norm, how can a free office wannabe solve a problem that the mighty MS Office can't solve? Simple: as highlighted by Michael Meeks at FOSDEM earlier this year, LibreOffice wants to have the largest possible list of supported file formats so that they can support their users in reading their old documents stored in long forgotten format and hopefully migrate them to modern and preferably open document formats. As a result, LibreOffice supports MS Works and MS Word out of the box.
So back to my mum's document, retrieving the content was then very easy: copy the document to a USB key, open it on my laptop using LibreOffice, save it again and copy the new document back to her PC. In this case, it meant saving it back as an MS Word document. In an ideal world, I would have saved it as ODF and installed LibreOffice on her computer but I'll leave that for another day.
So if you have any old document lying around that you can't open anymore, try LibreOffice first, you'll be surprised how many weird and wonderful formats it supports. If it still doesn't work, consider contributing a filter to the project or at least reporting the issue and providing sample files so that the developers can build such a filter.