I m currently having an issue with an Excel file on Windows XP Laptop. A user was working on this file yesterday evening with no issues.File was being saved to a network drive and no file save errors were received.When the user came in this morning the file was coming up with a eror message"excel cannot open the file because the file format or file extension is not valid" And also the file is showing up as having 0kb. Tried an excel repair on the file and also opening up in another program like .doc or .txt. Is there any way of finding out what happened this file or fixing the issue. Another user has also reported that the exact same issue happened them last week!!File server is running windows 2003 server. Shadow copies are available and I can restore the file to previous version, however the user did alot of work after that time.