You don't say if you are using Windows or Mac OS or what version... or what you meant by "munched" data.....
Just today I was reading a computer magazine and they recommend a free program called FreeUndelete.
http://www.officerecovery.com/freeundelete/
A couple of things.. FIRST: quit using the computer that has the data you want to recover. Every time you use it you risk the computer overwriting the data. The data may still be there, it is just that those particular sectors of the hard drive have been flagged by the MFT (Master File Table..think of it as a table of contents for a book) as available to use for new data. This software looks for those flags and then sees where the actual data is stored (all over your hard drive). It then reassembles the data into new files...and you can see what was recoverable and what was not.
Second you will need to download the undelete software to another computer (for reasons above). You can then transfer the software to a USB jump drive. Then remove the USB drive with the undelete software from the second computer and plug it into the computer with the hard drive you want to recover data. Run the program from the USB drive and follow the instructions.
Third... BACKUP the data to yet another external hard drive (or web based storage service). I lost 10 years of Money data because my hard drive and my floppy (3.5 in) disk...both of them...were garbage.... after that I quit balancing my checkbook. I do my budget in Excel.
...the magazine that I got this from also has a Help Desk for subscribers that I have found to be very reliable...so if the publishers are recommending this software I would trust it. Haven't had need for it yet, but glad it is there. Hope this is helpful.
Snakes ()