I have an excel file in which I track my family's finances. I access it
several times per day. When I started up my computer this evening and went
to open the file, it opened up empty. None of the worksheets are present.
It is identical in content to a new (i.e. freshly created) file. When I
examine the file properties, the date created suggests that it is the same
file I have been using all year. The file name is unchanged. But the file
size is only 13.5KB, the same size as any other brand new, empty excel file.

Any thoughts on what might have happened or how I recover this file?

For what it's worth, when I started up the computer this evening, it
displayed a number of inexplicable problems. The most persistent of them
was that I could not click on a single file/folder within a parent folder
without several other files/folders also automatically selecting themselves.
I don't know whether this has any bearing on the problem.

As this is a critical file, any help would be greatly appreciated.

Thanks,
Danny