It seems like you're encountering an issue with Excel cells losing their equations after upgrading from Windows Vista to Windows 7. This is an unusual problem, but there could be a few reasons causing this behavior. Here are some steps you can take to troubleshoot and potentially resolve this issue: 1. Compatibility Mode: Try running Excel in compatibility mode to see if that solves the problem. Right-click on the Excel shortcut, go to Properties, and then the Compatibility tab. Enable compatibility mode for Windows Vista and see if the issue persists. 2. Repair Microsoft Office: Sometimes, a repair of the Microsoft Office suite can resolve compatibility and functionality issues. Navigate to Control Panel > Programs >...