I accidentally saved over an excel document. Can I retrieve what I saved over?

Solution
You've got one realistic chance. Right-click the file, open its properties, and click on the Previous Versions tab. That accesses Windows' shadow copies. It's turned off by default, but who knows - you may have gotten lucky and some program you installed turned it on. With shadow copies, changes to a file are saved as a new file, so the original is still recoverable.

If the old file was incredibly valuable, you can resort to a sector search for a term which was in the file. When you overwrote the file, the data in the first sector was overwritten with the new file data. Subsequent sectors could have overwritten the old file or not. If you can find a sector which used to belong to the original file, a recovery program can search...
You've got one realistic chance. Right-click the file, open its properties, and click on the Previous Versions tab. That accesses Windows' shadow copies. It's turned off by default, but who knows - you may have gotten lucky and some program you installed turned it on. With shadow copies, changes to a file are saved as a new file, so the original is still recoverable.

If the old file was incredibly valuable, you can resort to a sector search for a term which was in the file. When you overwrote the file, the data in the first sector was overwritten with the new file data. Subsequent sectors could have overwritten the old file or not. If you can find a sector which used to belong to the original file, a recovery program can search every other sector to find the sectors which went before and after that file. You won't be able to recover the entire file because the first sector (and maybe more) is gone, but you may be able to recover some of your data.

Unfortunately I haven't tried to do this in over 10 years, so I can't point you to any software which can do it.
 
Solution