Since I have a copy of Excel, I’m having a hard time helping my friend fix his computer problem:
When he opens an attached excel file it has become associated with Adobe reader and he gets an error message.
You can download an Excel viewer at microsoft.com, if that’s what you’re hoping for. To change the file association, I think we’re going to need to know what version of Windows.
Have him save the document to his desktop, then hold down the Shift key, right-click it, go to Open With, Choose Program, select the appropriate program, and check the Always use this program to open these files box. This works on all recent versions of Windows.
In addition to the viewer which KneadToKnow mentioned, another option would be to install OpenOffice and associate .xls files with Calc.
Google also offers a free online spreadsheet program that you can upload .xls files to and manipulate. The site is http://docs.google.com
Number’s solution to the file association issue is excellent, widely applicable, and I’m embarrased I didn’t suggest it myself.