Comment by kbenson

> MS Excel from back then won't run on anymore, 16-bit apps aren't recognized by modern Windows, etc.

They certainly will run, even if only through emulation or API conversion. In fact, that's probably what modern MS Excel does to old XLS docs, which is convert them to an in memory format that probably more closely resembles The Office Open XML format than the Excel Binary File Format (the extension may or may not change, but the format did).

> I posit that .XLS is a more stable platform than Windows itself.

Well, ignoring that we've drifted quite far from hardware, I would say that Excel (which would be the actual platform, not the container format) is not a general purpose computing platform (at least not a feasible one), not something that necessarily defined what architecture is being used, except tangentially.