Doubtful as the 7 install will have overwritten them. There may be some recoverable files, don't install anything else until you've looked as you will only destroy more. Recommend you use another PC to download and burn to disk Hiren's Boot CD and try the Data Recovery tools. (Recuva seems to be very popular). As this boots your machine from the CD (once you change the boot order ) it will not further damage your lost files. http://www.hirensbootcd.org/download/
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After formatting the system with windows xp & Installing windows 7, is it possible to recover files and folders in c drive ?
Apparently, your installing Wins 7 files may have rewritten part or even all of your original files or folders. You should prepare for the disappointment.
But, now, as the other persons writes, you also could take some recovery tools to have a try.
I know a drive recovery freeware that may help you: http://www.formatrecovery.blogspot.com/2013/02/recover-...
If I remember rightly, this free one specially provides a "Format Recovery" option in the main interface to the customers to process their format recovery problems. It is worth a shot!
In the future, you should be much careful before you decide to do some changes to your important data. At least, you should make a data backup well.