Trouble opening file

[piggylumps]

Can anyone help?

I've been working on a file for 6 months now, came to open it today and I get an error message saying the the "file format is not valid"

This was last opened and saved yesterday with no trouble at all. Has anyone else encountered this and is there a way around it so I can get in and save it as something else?

 

[VoG]

This may help you http://support.microsoft.com/kb/820741