Microsoft definitely hold some blame here. If newer versions of Office could competently display old Word documents, there'd be no need for the mad scientist virtual machine solution. (I wonder if they have to buy a licence from MS for every version of DOS/Windows/Office they need to use for this? ;-) )
MS chose to rework .DOC format for every new version of Office, forcing people to upgrade, and now they get to benefit from a bit of PR fluff about how they're making it possible to read old documents. Gotta love that lock-in.
But MS aren't solely to blame, they're just one of many peddlers of closed formats over the years, and this is a perfect example of why vendor-dependent formats are trouble waiting to happen. At least these days we have a couple of options which aren't tied to any one OS, software package or vendor and stand a good chance of being readable in the future. TNA need to be converting everything they can into such formats, starting now.
The hardware most certainly *can* be an issue. I may have a 3.5" floppy drive in my current system, but no standard PC floppy controller can read the Amiga's native disk format, so anything I didn't transfer when I *had* a working Amiga is now trapped on unreadable media. Luckily none of it is important enough to jump through hoops to recover, but TNA's archive is of significantly more importance to the national record than my A-level coursework is...