... when you don't have the right software (FTM).
Last week, I was very generously sent a CD of his research by a contact who found my website, so that we could compare notes and combine our research.
When it arrived, it hadn't been saved as a GEDCOM in a way that I could open in Family Historian.
Rather than just telling him I couldn't open it, or asking nicely on here for someone to open it and export it for me (I didn't know which version he had used), a bit of googling for help/inspiration, took me to the Family Tree Legends site.
The software is now a free download and it let me import a FTW file and then export it as a standard GEDCOM and then open it in FH with no problems.
If you are looking for free family tree software this is well worth looking at. It is linked to the GenCircles site, but you don't have to use the internet connection. If you are a FTM user, it could also help you in easily making a GEDCOM which will load into our GEDCOM database.