Have you reinstall Windows on your first partition? Is it the same size? You might try the photorec program to recover the image. You shouldn't use this computer anymore, or at least don't use windows if the thesis is located in your new C:\ partition. If new files were saved over the location of the old files, then the covered files are lost. If the files you want are located in unsaved areas, you may be able to find it. It's also possible that parts are overwritten and parts aren't.
The first thing you should do is create an image backup of the partition. If you have resized or relocated the partitions since the thesis was overwritten, then create an image backup of the entire drive.
Google for: photorec testdisk site:sourceforge.net
This article has links to both:
http://lwn.net/Articles/290562/
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What kind of files is this thesis saved on? If you are composing it in LaTeX or another text file, you could use Grep on the partition device to locate a pattern you know is in the file. E.G. '\document' or perhaps for the title.
example:
grep -ob --binary-files=text 'http://www.novell.com/products' /openSUSE-11.1-DVD-x86_64.iso
51315943:
http://www.novell.com/products
51318020:
http://www.novell.com/products
This can help you zero in on where the file is. The number at the start is the zero based offset to the match. If the file is contiginous, and you can locate the start of it, you can use "dd" to cut out a part of the partition where the file starts. Then work on cutting off the excess to gain the original text back. You would be using the device node of the partition or drive instead of a file name.
This type of thing is a last resort when you can't recover the file itself.
Another thing to consider is to use losetup to attach a loop device at an offset, and then using the file command to identify what was found if anything. You could do this in a loop and filter out lines where nothing was found. You might try this is you already got a hit using grep and are trying to zero in on the start of the file.
It might look something like this:
Code:
for ((offset=1024;offset<=10000;offset+=512 )); do
losetup /dev/loop1 /dev/sda2 -o ${offset}
file -s /dev/loop1
losetup -d /dev/loop1
done | grep -v ': data$'
/dev/loop1: SysEx File -
The last line is a sample results running the code. The file command analyzes the type of file based on the contents, so you can use it when you don't know the filename or extension. I should really be doing this on a file image of the drive, but I'm not going to do that for a live example. Instead of /dev/sda2, the name of the file would be used.
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Good Luck, but next time, perform backups and have copies in different locations. External drives, cdroms, pendrives, etc.