RootsMagic, the newer genealogy program compiled by the author of Family Origins will open and convert FOW 4 databases to it's own format. (It cannot handle FOW 4 backups, however.)
There was only one problem with FOW moving from WIN 9X to Win XP that I am aware of, that was thet it couldn't handle exporting GEDCOM files to the newer, larger hard drives.As long as the drive, or partition, was 2GB or smaller there was no problem. I think that this wis fixed with FOW 9.
As for problems going to Vista and beyond, I haven't a clue. I would assume that later programs are more likely to handle the transition with more ease.
Upgrading to RootsMagic to convert your data to a later format ould help some. (It also has some good report formats for printing) A good GEDCOM file, stored on long term media. (You can hear all kinds of stories about the longevity, or lack thereof, of different media types. Who do you beleive?) But, for really long term storage, a good printout, using acid free paper and non fading ink would probably bee the best bet. I have a rather large family folder which was created with an old thermal copy machine, back around 1970. It has faded so that some of the pages are completely unreadable. The backup and GEDCOM files DO NOT contain any pictures you have linked to your data. They will have to be saved separately.