You will need a piece of windows specific software that is smart enough to do a NTFS scan / recovery of the drive. I would ask to have this moved to SuperUser - the expertise there would be most helpful in getting you better options.
Above all - eject and disconnect the drive and keep it powered off until you have better advice.
In the mean time, perhaps call a professional house and get a quote. They will have handled this situation many, many times and might have better tools / more training to get a better recovery. They will charge for their expertise and time handsomely.
I would suggest:
You just have a translation error as well as an over-write situation. If you have an idea how much space was filled, how big the drive is, and what proportion the mac overwrote - that will help the professionals estimate if you will get anything useful back. Think of a shotgun pushing pellets over a poster. A few - and most of the poster remains. The more overwriting, the less change the picture you want to recover will be able to be recreated / or rescued in partial form.
The good news is it won't need a clean room recovery - the drive is operational, just a change of the file structure as well as over-writing of data. That will let you decide to get PC based software and attempt a recovery yourself or pay or just write this up to "sometimes spring cleaning comes in the fall".
There are also low cost options - buy a new bare drive and an inexpensive USB/SATA adapter and you could make a block copy of the drive and test out whatever idea / DIY software knowing you are working on a copy of the drive - not the only copy of the data.