On this site you will find products to help you remove forgotten passwords, both free and PRO versions.
There are several passwords in Excel. The 3 first on this list are covered by the Excel Password Remover:
1. A password for each sheet that protects cells from editing and/or viewing
2. A workbook structure password to protect hidden sheets and the sheet structure of the workbook
3. A sharing password for shared workbooks (not so commonly used)
4. A password to open your workbook. For 97/2000/XP/2003-files I can recommend this one: Excel Password Recovery Lastic. Excel Key can also do that, but also attempt password recovery of Excel 2007/1010 files.
5. A password that protects the VBA code. Solutions here and here
Excel Password Remover removes the password protection applied by the “Protect sheet” and “Protect workbook” commands in Excel (i.e. enables you to edit the workbook even if you have forgotten your password).
It works on the active workbook, so you must be able to open the workbook in question.
It will remove passwords of any length, also passwords containing special characters. The free version is for personal use only. The PRO version is for business users, and others wanting the extra functionality.
Recommended links on the right contains links for other password needs.