If you cannot open an Excel file and see Excel cannot open the file because the file format or extension is not valid error, see this post.

2. Select Manage Workbook > Recover Unsaved Workbook . Excel file recovery options 3. From the list of files displayed, open the inaccessible file and save it. Solution 7: Open MS Excel in Safe Mode ...

How to Convert DAT to Text in Excel. DAT files are files with an extension that isn't associated with a specific application or program and can be almost any type of file including video, media or ...