Sadly one of the file servers I have used extensively for hosting videos, pdfs, spreadsheets and the like has gone the way of many free things on the internet, and this means that a number of links in older posts will now be dead. Please accept my apologies for this.
But all is not lost. I'm glad to say that everything has been transferred to other servers, however it will take some time to work through all the affected posts and update them, and there'll probably be some that I'll miss. So if anyone does come across a broken link, would you please let me know about it by leaving a comment here.
The same applies to broken links to other sites. I've usually managed to keep copies of the external web pages and externally hosted documents I've linked to, so I'll be able to put these copies up on one of my servers and link to them instead.