[Zoolook]

Sounds like a corrupted xls file.

Anyway, go to the fider, find the file and ctrl/click (or two finger click) onthe file and select "open with". Select 'other application' and then find 'text edit' which will be in your application folder, or just type it in the search window in the top left.

It should open, but might look like garbage. Anyway, if it does open, resave it as <filename>.csv then open excel and import the csv, and try and sort the data from there.

If it doesn't open in text edit, then it's probably beyond recovery.