If you don’t have any Microsoft Office or Microsoft Visio software installed, you can download and use these free Viewers from Microsoft to view Office file formats like, Excel, PowerPoint & Word or Visio files.

Excel Viewer lets you open, view, and print Excel workbooks, even if you don’t have Excel installed. You can also copy data from Excel Viewer to another program. However, you cannot edit data, save a workbook, or create a new workbook.

PowerPoint Viewer 2010 lets you view full-featured presentations created in PowerPoint with full fidelity. This viewer also supports opening password-protected Microsoft PowerPoint presentations. You can view and print presentations, but you cannot edit them in the PowerPoint Viewer.

Word Viewer lets you view, print and copy Word documents, even if you don’t have Microsoft Word installed.

Microsoft Visio 2010 Viewer allows anyone to view Visio drawings and diagrams, created with Visio 5.0 through Visio 2010, inside their Microsoft Internet Explorer  Web browser.

Go here to see the complete list of Microsoft Office Online File Converters and Document Viewers.