: You may need to run the .exe in compatibility mode for Windows XP (Service Pack 3) or Windows Vista .
Many forums claim you cannot activate Euro 2008 anymore because EA shut down the servers. This is partially true for multiplayer, but if you use a verified key. The trick is you must install the game from the original disc image (ISO) and use a patch to bypass the phone-home authentication. A verified key ensures that when the game does a local hash-check, it doesn't flag your copy as pirated.
The CD key is a unique 20-digit code found on the back of the game's manual or inside the original physical DVD case.
You can still purchase physical "Big Box" or DVD-style cases from collectors on eBay or Amazon. These often include the original manual with a verified CD key printed on the back.