Error Message?

I have a MacBook original [not pro] and I tried to install a very simple application called "Happy House Virtual Rodent" it's not highly important that I install it... but I was hoping to get it to work none the less. It seems to install properly but when it appears on my screen, I get a no symbol (the circle with a slash through it) and that is it and it is a greyscale image. When I tried to open it, I got the error message "You can not open the application Happy House because it is not supported on this system" however, I know it is specifically encoded for Macs. The only errors I can think of that may have caused this- are that it is a kind of old program and may not work on newer Mac computers and also that the application is ".sea" not being a huge computer person I'm not sure if that makes any difference. Can someone tell me why I'm not able to run it and/or how I could possibly run the application?