Some documents can only be viewed using Microsoft Excel. However, if you don't have MS Excel, you might like to try Microsoft Excel Viewer - a free piece of software that allows you to view (but not edit) these documents.
Microsoft Excel Viewer is a piece of software that enables people who do not use Excel to view and print spreadsheet files exactly as they appear in Excel, but it does not allow them to edit the spreadsheet. This small, freely distributable viewer gives users the flexibility to view page layout, copy and control cell sizes, and access the zoom and AutoFilter features. This viewer also supports OLE DocObject as well as the ability to view any Excel file.