Many thanks for all the great responses, guys. Really appreciated!
@Ashtoreth: Yes, I did purchase it through Humble. As you say, no specific system requirements there at all. Let alone a statement that can't even install the game on anything less that Vista.
I can fully understand having a minimum spec for performance reasons. But to stop you from even running the installer after simply saying 'for Windows' on the purchase pages is a bit daft. As it is, I'm running a rig of a spec that could quite easily toy with MFP in one hand while doing something more important with the other, so it grates a little to not even be allowed to install the game.
If Frictional don't want to support XP, that's fine, I've no problem with that. But I should at least be able to install it and try it out.
@Pluto: Wow... Many thanks for taking the time to write all of that out. That is very much appreciated. Thank you! Sorry to hear you had the same/similar issue, but hopefully you're all sorted now.
I shall have a look at doing what you suggest and report back...
@Diz: Much appreciate you taking the time to reply and for your comments. Thank you.
Yes, service pack 3 here.
True, XP is now a legacy O/S. But it is still recognised professionally as a solid O/S (I actually work in the IT industry). Vista, on the other hand, is rather....er, maligned. Windows 7, on the other hand, is what Vista should have been in the first place.
I guess it really just seems a little odd to even stop one from installing the game, let alone running it, (unless it's hard coded to DX11). I mean, here I am, running Skyrim on max settings with nearly 200 mods and an ENB and experiencing rock solid 60FPS in big battles, and I'm being told that I can't install MFP...
Seriously, guys. Don't support it if you don't want to. That's fine. But at least let me try it out...
Anyway, I shall give Pluto's excellent suggestions a go and see what I can achieve...
Once again, thanks for the replies.