How to open password protected excel file???
The answer depends on the type of the password and the format of your document. Here is a small article where different variants of your problem are considered: http://passwordexperts.com/Choosing-Excel-Password-Recovery-Tools.htm
Assuming you are intended to receive and view the Excel file my first suggestion would be to ask the person you got it from for the password.
Other then that some options have already been listed.
S1-Protection Excel Add-in: Free evaluation version
Hack into a protected Excel 2007 or 2010 Workbook
Here is some software that I found that may be able to help you. Download at your own risk and please scan them with your local anti-malware solution before installing.
Excel Password Recovery v2.0
Excel Password Remover
How to Remove, Crack, or Break a Forgotten Excel XLS Password
Excel® Password Remover
Free Word Excel and Password Recovery Wizard
Free Word / Excel Password Recovery
As a last resort, password protected XLS files are vulnerable to intelligent bruteforcing and hex editing attacks. However, this can take a lot of time depending on the length of the password.