If you are looking for ways to open the new Office 2007 files you can install the Office Compatibility Pack and it will enable your Office 2003/2000 installation to be able to work with the 2007 version of the files.
The original link to Microsoft:
You can also download and install OpenOffice which will give you access to the Microsoft Files and be able to create / edit them for free. OpenOffice is available free under the GNU / OpenSource stuff at: http://www.openoffice.org