1. Hold the Windows orb key, and press 'R' to open the 'Run' dialog window.
2. Type the exact phrase in the Run dialog window, including quotation marks:'C:\Program Files\Microsoft Office\Office12\excel.exe' /regserverIf you installed Excel 2007 in a different folder, adjust the path accordingly. If you are using a 64-bit version of Windows 7, change 'Program Files' to 'Program Files (x86)'.
3. Click 'OK' to have Excel register itself as the default program.