They have already proven it by their "countless testing machines"....

Yeah, good luck going up against those.

I know that. But as I've said, I already did this like 5 times. Everytime I want to buy a new DLC for Crusader Kings 2 I have to manually check which ones I already have.

IT DRIVES ME FUCKING MAD.
Oh yeah, you're right.

Also, I believe Windows Vista and 7 are not listed as supported OSes on game page...

Besides, if i purchase a boxed copy or a digital copy with or without DRM, the result is identical, i purchase the licence to use the product. Physical media will be mine, content is copyrighted to their original authors. Digital media, i can keep the installer files on my hard drive.. I don't see a difference beside DRM which is trivial in most cases unless for hardened crybabies with a possession obsession over data files that are not their own to begin with. Consumers buying a right to watch/play/use this is it.

And GOG doesn't even let you add games to your cart unless you specifically want to make a gift cart. Buying is a lot smoother on GOG than on Steam.

Yeah, that 'feature' of Steam isn't exactly helpful when browsing the store. I decided long ago to list all my games and DLCs in a text file and just pop that open when browsing games/DLCs. Makes it far easier on my head. (I have 2 monitors, so have the text file open on one while browsing on the other).

And is it just me, or does The Joe seem a bit grumpy today?

That is actually interesting. Can you simply assume that? You can probably argue both ways. With GOG, again doing it better than Steam, it is pretty clear if a game is supported by an OS.

Because "minimum requirement" is very complicated with OS.

I just checked and Steam has also changed this with newer games, dropping the "Minimum" line. But with Jade Empire you can argue both ways.

What problem are you having with JE, is it a dll error?

Isn't this ironic, considering which store wishes to store your payment information to make payments go smoother?

What kind of steam are we talking about?

To OP: If it doesn't work with what I posted earlier you could resort to a fixed .exe as this game is single player and doesn't seem to support achievements so not the end of the world. The one I tried with is released by Vitality but you'll have to find it yourself.
Dude!!! You didn't try everything. Come on, go back and read my post.

Here it is: SOLUTION

Listen, I did this like 2 hours ago. It didn't work for me either by adding admin to all exes. including Steam but after I added the file that I mentioned that bypasses the Configuration file it works!

You are correct. Only XP is listed. For anything else, all bets are off. As I mentioned though, it runs just fine on Windows 7 in my experience.

I get the impression the OP did not read the system requirements or perhaps notice only XP listed. A good rule of thumb which I suspect is obvious to most of us here is to check the Steam forum in a case where your OS is not specifically listed to see if people report the game runs okay. It also wise to do this anyway just to see if people are reporting any sorts of issues, particularly in numbers.

I wouldn't buy anything on Steam without doing that. If failing to do that is what happened here I think the OP needs to try and learn from the experience and also to seek help in the forum in solving the problem they are having.

To say even more, unless they changed that, steam wishlist doesn't automatically delete items you already have. It makes your wishlist a huge mess. after some time it's filled with games you already have but forgot to manually delete.
But SimonG said, and I agree with him ( :P ) that Windows XP is listed as a "minimum requirement" , not as a "supported".

So... "you could argue both ways" :P

Avoid the config utility altogether

You can do full config in the game itself. Literally, when you hit play just launch, don't select config tool.

Also with some of the older games if you start the Steam client with right click run as admin (You will get a warning about running Steam as admin but just ignore it) then launch the game and it registers the game dll's correctly for future use. Once you have run it once exit game then exit Steam and just restart as normal (Had to do this with Hitman Blood Money to make it work)

Hmm, I'm in OS X atm so I can't look at the launcher buttons. Does the config utility run from the launcher? I am forgetting because if I ever used it at all, it would been one time when I first began playing. I don't think you actually need it though since you can change resolutions and whatnot within the game's options menu once it is running. I wish I could fire it up now to see it and be sure I am right about that but I think I recall adjusting settings once I was into the game.

I also think I recall (this is bad, it was only two weeks ago!) needing to grant admin rights to the launcher and then all was good.

Are you able to get the game to launch to the opening screen? And if so, can you take a look at the options within the game and change them? If so, you ought to be golden.

It is a good game. I've been having fun with it. It's worth the effort to try and get it working unless you are just burned out at this point on it. Maybe you could revisit it later if so. I can tell you it works on Win 7 just fine for me which says to me it ought to be able to start up for you as well.

If giving the launcher admin rights doesn't work, I would suggest giving admin rights to the game's executable file as well.