As DeMignon said, you might never be able to run it on Windows XP SP2 64-bit. At this case, you can upgrade to Windows 10 64-bit, but as a Windows XP user you'll have to pay (in cash) to get it.

Obtaining a copy of Windows 8 or 7 (your next preferred options) will be a bit tricky as you'll have to hunt down for the discs containing them...or pirate them. Whereas with 10, Microsoft is selling it right off the bat with no hunting involved. However, if you want to hunt for 7 or 8, go ahead, as these versions are supported by GOG Galaxy no problem.

That's it. You can't do anything about it with tweaks or whatever, you'll just have to bite the dust and upgrade your Windows version, if you want it now.

Your other choice, which involves a lot of waiting, is to wait for Galaxy to hit Liunx, and then install a Linux OS to use it, though be careful with the compatibility. Or you can actually use the Windows Galaxy with Linux using Wine, that works too.

Obtaining the discs is relatively easy, it's getting a valid key that's becoming difficult.

That's true. You need to hardware to run it though. See above.

Those look like pretty good deals, I sure haven't seen anything that cheap in the (many) places I've looked. Also, did you mean upgrades to the used PC immediately, or in the future? Sorry if I came off as rude. It just irritates me when people don't seem to take the cost of computer into account.

Another option to avoid running XP is use Ubuntu or Mint or something.

Oh, that. I forgot that torrenting a Windows 7 or 8 ISO is still okay, what becomes a legal gray area is where you get the Windows key. Right.

Well over a decade later and there are still people acting all amazed whenever they find something that doesn't work on Win XP 64.

I didn't think that there was enough amazement in all the world for that.

Forget torrenting, use techbench and a script. See here.

win 7 hardware isnt that expensive
i bought a 10 year old laptop for less then 40 bucks and it can run windows 7 just fine

( ironically i want to use it for xp and run older games on it but regardless it runs 7 without a hitch )

that was my point actually
it looks like mozilla but identifies as firefox

Have spent the last week or so attempting to install Win7 and then Win10 on a ton of older machines. Windows 7 can be installed on most of them, though some of the laptops do miss drivers. Should you decide to take the plunge and want info, do send a message, but be aware of the timezone I'm in.

Shit. I take it back. It turns out the OP is onto something. I just tried and there's no way at all to install Galaxy onto my Amstrad CPC 464. How can GOG hope to justify its existence when it doesn't support overpriced, under-performing ludicrously obsolete platforms?

yeah an 10 year old laptop with an celeron and 2 gig of ram i recently bought for around 40 euro
came with windows 7

and 7 ran remarkably well on it
you dont need a beast of a computer to run windows 7

As it wore, a graphics card to run most GOG games (the older ones anyway) might run you about...20 USD. :V I'm completely serious. But of course, bigger ambitions do mean a bigger price.

... and it never will.

Not with Linux, unless he has some very obscure win-only soundcard or something. And then he could probably find a post on some forum somewhere on how to roll his own driver for it.

At the moment there is no requirement to use Galaxy, so count that as a blessing.