You can find some free recovery software here: http://pcsupport.about.com/od/filerecovery/tp/free-file-recovery-programs.htm
Please bear in mind that although it's often possible to recover files which have been accidentally deleted, it's a different matter when Windows has been re-installed on the same partition where the required files were.
Installing Windows overwrites everything on that partition, making it very likely that all the old files will be damaged and not usable. The files you want may not even exist anymore. You should have kept backups on a different drive.