+1 for Wine. It is not an emulator ("
Wine is
Not a
Windows
Emulator") it is a "compatibility layer" - there is a big difference (especially in performance terms)!!
Wine HQ
It should be in the repositories for Ubuntu and other major distros. You should however go to Wine HQ and add follow the instructions for adding their file server into your repositories. That way your GNU/Linux package manager can download the latest version. It has massive stream of bug fixes going into each revision (but just beware 'cause this fixes can break other things - so called "regressions").
Wine is very easy to use. You can use it on the GNU/Linux GUI desktop by associating ".exe" files to Wine. Then you should be able to just double click on the MS Office 2007 "setup.exe" file. On the BASH command line you just type "Wine <windows command>".
Wine creates a virtual "C" drive in "~/.winerc/C_drive" I think. You can navigate this by typing "Wine explorer.exe" - BASH shell (or make a shortcut on the programs launcher - if it isn't already there).
It does great at running a lot of games (if you have an Nvidia GPU anyway) however things like MS office are a much bigger challenge for Wine as MS Office is obviously much more tightly coupled to the Windows OS APIs.
Bob