You can edit Excel files with the Excel Web App from anywhere without having Excel installed on your computer.
1. First, save an Excel file to your Windows Live SkyDrive.
2. Go to office.live.com and sign in with your Windows Live ID.
3. Click a file name.
The Excel Web App opens the workbook in the browser.
4. Edit your Excel file.
Note: there is no need to save your file since all changes are being saved automatically. Not all features are available in the Excel Web App.