First. When caught in a boot loop, boot into safe mode. Often safe mode will let you get your files before you do something like reformat.
That said I don't have a specific program I'm going to reccomend, just a catagory.
You need a program that finds missing files. Some of these programs are simple. Files leave traces in the hard drive tables (wrong word). You need one that will look at the data on the drive itself. That's a more advanced version of a file recovrey program. Norton Utilities can do this. I don't know if the free versions of file recover at this good yet. Some may be.
My partner installed xp sp3 and ended up in a continual reboot, she then pressed F10 which reinstalled xp losing all her files, is there any way of recovering these files??