View Excel 2007 Files without Microsoft Office
You got an Excel 2007 spreadsheet in your Inbox but there’s no Microsoft Office on you computer to open that file.
You could either buy Office 2007 or just grab the free Microsoft Excel 2007 viewer that was released this week. This program has been available since long but only the new version supports the xlsx format.
With this new Excel 2007 Viewer, you can view and even print spreadsheets created using any version of Microsoft Excel. You can also copy data from Excel Viewer to another program.
The other option for opening xlsx files is the Office Compatibility pack but that works only if you have a copy of Office 2003 or Office XP.
Excel Viewer [Microsoft Download Center]
Related: Convert XLSX to XLS [using Zamzar]

Wrong! Earlier Excel Viewer + Compatibility pack = XLSX viewing ability
Amit I’m quite disappointed to see the most basic of tips from you. Word, Excel, and PowerPoint viewing applications have been around from quite a while now, at least 3-4 years, maybe more.
But then again, its your blog so you rule. As for me I’m just a reader.
Ed: Manu - This Excel 2007 viewer was released very recently with support for XLSX file. This is big because there’s no other alternate software to view Excel 2007 spreadsheets.
Because XLSX, docx etc. are new formats, MS was bound to release their viewers as well.
BTW i think Zamzar (zamzar.com) lets you do this.
Using the Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats Office 2K3 users can view and save files as O2K7 formats.
Does OpenOffice support the new excel file format yet? I don’t deal with excel files much (thankfully) but it’s always worked fine in the past for me.
I received a .xlsx and .xlsb spredsheets attached to emails. I have Windows XP with Office 2000. I have been trying to open each of these after I have downloaded several different updates including Excel Viewer. All I want to do is open one of these files in a .xls format so I can see it. I don’t want to buy a new program when I am happy with what I have and don’t use it very often.