Help: Different Excel file formats and Excel versions
Open, View and Print 2007-2010 files in older Excel versions
I do not have Office 2007 or Excel 2010 on my machine, how can I view and
print files saved in one of the new file formats ?
Download the Excel Viewer from the Microsoft site

Brief Description:
With Excel Viewer, you can 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. This download is a replacement for Excel Viewer 97 and all previous Excel Viewer versions.
Here are the links to the Word and PowerPoint viewer
Download the Word Viewer
Download the PowerPoint Viewer
Open, Edit, Print and Save 2007-2010 file formats in older Excel versions
I do not have Office 2007-2010 on my machine, how can I open, edit, and save documents, workbooks, and presentations in the file formats new to Microsoft Office Word, Excel, and PowerPoint 2007-2010?
Download the Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint
Brief Description:
Open, edit, and save documents, workbooks, and presentations in the file formats new to Microsoft Office Word, Excel, and PowerPoint 2007-2010.
Note: With this Compatibility Pack installed you also have a few more options in he Save/Save As dialog.

Convert 97-2003 files to one of the new 2007-2010 file formats
You can open and edit 97-2003 files in 2007-2010 without problems, but if you want to use
the new things in Excel 2007-2010 like for example more rows and columns you must use
one of the new 2007-2010 file formats.
For a few files you can open the 97-2003 file in Excel 2007-2010 and use SaveAs
on the Office Button or File menu to make it a 2007-2010 file.
Remember that if there is code in your 97-2003 file you must SaveAs xlsm file and not as xlsx.
If you want to convert a lot of files check out the information in Debra Dalgleish's blog
http://blog.contextures.com/archives/2008/08/28/office-2007-bulk-file-conversion/