Wine is a translation layer that makes it possible to run many MS Windows applications on GNU/Linux and Ubuntu. Unlike using an emulator with Microsoft Windows Wine won't slow down on you. It has the ability to run applications at native speeds.
For information about Wine see:
You may also want to consider supporting Wine development by getting an easier to install and well supported version from CodeWeavers. CodeWeavers releases CrossOver Office which is based on Wine. It includes support for very specific in-demand applications and guarantees continued compatibility with these applications. For more information see:
http://www.codeweavers.com/products/cxlinux/
If you are looking to play games CodeWeavers also puts out a version of Wine specifically designed to play many popular MS Windows games called CrossoverGames.
http://www.codeweavers.com/products/cxgames/
If you need assistance with Wine, CrossOver Office, or CrossOver Games contact support.