If you have an .xlsx file attachment in your email inbox but the computer doesn't have Microsoft Office installed to open file of that extension, what are your available options?
The xlsx file format is the default extension for spreadsheets written in Microsoft Office Excel 2007 and Office 2010. The format is currently not support by GMail attachment viewer or any of the online office suites like Google Docs.
However, you can easily convert .xlsx spreadsheet to the traditional .xls format using the Microsoft Office compatibility Pack available here. This will help you open, edit, and save .xlsx files in Office 2000, Office XP, or Office 2003. More details on Office 2007 FAQ.
Alternatively, you can convert .xlsx to .xls or any other text format online using the email conversion service of Zamzar. Just forward the email attachment to firstname.lastname@example.org or email@example.com and it will send you a link to download the converted file.
Unlike the Microsoft compatibility pack, the Zamzar .xlsx to .xls conversion services will not require a copy of Microsoft Office on your computer.
And if you have OpenOffice, Zamzar can also convert the XLSX file to OpenDocument spreadsheet format.
Also see: Open .docx Files Without Word 2007