Never attempt to open a save by double-clicking it. You have zero chance of the game opening and loading the save. Your computer will attempt to open the save with whatever the extension of the file is linked to, which usually has nothing whatever to do with the contents of the save or the game it's for.
You need to put the save in the game's save folder, start the game, and load the save from there. If you don't see the save, it may not be compatible with your operating system.
and i still haven't been able to down load my save game. headscratch can you tell me how i can down load the save game ?
You aren't making sense. First you say you tried to open the save by double-clicking it. Then you say you haven't even managed to download it yet. Download means get it off the Internet. If you have it on your desktop or in your Downloads folder and double-clicked it, you've already downloaded it. The saves on the nicouzouf website are zip files, so I don't see how you'd get any message at all by double-clicking a link in your web browser.
If you need to copy the save to your save folder,
first find out where the game's saves are.
Despite that certain websites claim the Nostradamus saves are in
C:\Program Files (x86)\Nostradamus\Users\Profile1\
that doesn't look like a Vista/7/8/10 location to me. It looks like an XP location, and I'd look elsewhere if you don't see anything the Program Files location.
Save folders are most likely in one of the subfolders of
C:\Users\your-username\AppData\Local\
C:\Users\your-username\AppData\LocalLow\
or
C:\Users\your-username\AppData\Roaming\
Occasionally I've seen save folders in
C:\Users\your-username\Saved Games
The subfolder can be named after the game, but more often is inside another subfolder that's named after the publisher or developer.