can you tell me how to fix a compatability issue with windows 7

I have to ask , why, windows 7 preium, I have a presario laptop and am using separate monitor keyboard and mouse, I used to have windows xp on my desktop pc but have out of disk space issues, so I’m using my new laptop, currently am having compatibility issues with windows 7, my games won’t run , example Age of empires 3 shows error as incompatable with windows 7, it worked fine before on xp. is there any software out there that can help resolve issues and allow me to still play my favorite games, also Need for speed when I had win 98 never could work with windows 7 either please help me.