We recommend that all users of Microsoft Office 2000, Office XP, and Office 2003 download and install the following tool from Microsoft:
Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats
This tool allows users of those versions to read and write Office 2007 documents. It should be noted that this tool does not enable Office 2007 features on those systems — it only allows users to read and write the files.
If you do not have MS Office, you can download the Open Office Suite. This free shareware is compatible with MS Office.