I have verified that this method works in Windows 7 64-bit. A friend on Gamespot has verified it works on Vista as well. Commenter julio was kind enough to verify that this method also works in Windows 8 Enterprise, 64-bit edition.
Jade Empire needs DirectX 9 to run, and it is incompatible with any later versions. Win7 ships with DirectX 10, and that’s what causes the big error when you try to load the game. Thankfully the solution is simple. Before installing the game, click on the button on the installer that installs DirectX 9. After that has installed, install the game.
If you bought Jade Empire from Steam, or from any other place where you get the digital download and not the CD with the Dx installer, you can get DirectX 9 here. (Microsoft download, so it requires a valid and activated version of Windows.)
If you installed first DirectX9 and then the game, the game will now load and run, and run great. What it will not do however, is to save your progress. At all. Yes, I agree, this is a deal breaker. Fortunately the solution is simple. Navigate to the main game folder, un-creatively named “Jade Empire” and right-click on the file JadeEmpire.exe. In the right-click menu, pick Properties. Locate the Compatibility tab, click on it, and check the box to run the game in compatibility mode for “Windows XP Service Pack 2”. You also need to check the box to “Always Run As Administrator.” Click Apply and Okay and all that, until all boxes are gone. Now replace the shortcut on your desktop with a shortcut directly to this file, and use that to launch the game.
Jade Empire should now run and save, and load saves, just fine on your Windows 7 system.