I would use the suggestions above. There are 100's of different software titles dedicated to data recovery.
I found this, that may help you find a suitable program:
I've used GetDataBack after a reformat and it worked for me. However, the fact you installed Windows on top of the drive will have severely reduced the number of files you will be able to recover. If it ever happens again, try to stick the drive in another computer with windows already installed and do the recovery first.
Hope you get your files back, good luck