JeanGordini

There's a site known as ark.intel.com which will tell you everything about your CPU, especially if it supports 64-bit and such stuff. That said, I'd also perfectly possible that Windows 7 requires some obscure and little known instruction not present or activated on your CPU. Intel I'd very strong when it comes to segment their offerings. Meanwhile, Microsoft has dramatically improved its OS security and I wouldn't be surprised to see it had a few hardware requirements with it.

Does having the game's key mean it will allow preloading?

I'm a bit confused now. On Paradox's site, it still says it should run on XP. On Steam, however, it says you need a 64-bit OS to run the game. That would neatly explain the lack of Windows XP support since for all intents and purposes, there never was a 64-bit Windows XP. Actually, there was a Windows XP 64 bits, derived from Server 2003, but it was never released for the mainstream. Anyway, if your computer can run Eternity, it surely can run a proper, modern, version of Windows such as Windows 7 or 8.1, and you should update your computer, if only for Microsoft's software support.

I'm not a big fan of late stretch goals. I kind of fear they could somehow distract or delay the original game, its QA... Let's by a bit frank about it, as much as it saddens me to say it,Obsidian is mostly known because of their incredible writing skills and is also infamously known for less than polished releases. Obviously, some of them are mostly due to outside constraints but nonetheless, between a polished game and more content, I'll choose the polished game. I've nothing against seeing such stuff appear in whatever form extentions might take though.