If you bought the game through Origin, you can do the following steps

Game Properties > Advanced Launch Options >Command line arguments > Type this command -w

Keep an eye Take a look and disable Spore in Origin under Advanced Launch Options

The game should now open in windowed mode
Afterwards go to Spore in the graphics settings and let the game start in windowed mode. Don’t miss out this is an older game, it does not run under the latest screen resolution.