Day by day cracking is being a tough job. But yet very possible. Earlier a software may require a simple serial key to activate. But today there are many other options. Sometimes you might be asked to connect to the internet to activate or sometimes you're asked to make a phone call!
Microsoft Office 2010 has the same problem. It is not simply activated by the CD key. Sometimes CD key may not be asked during the installation process. If you're required to enter serial then try any of the following: