It has happened to me many times, formatted hardisks without backup, sometimes deleted the data unknowingly but, now you can recover such lost data with TESTDISK.

TestDisk is OpenSource software and is licensed under the terms of the GNU General Public License (GPL).

TestDisk is a powerfull FREE data recovery tool it can run under windows as well as Linux.

Here's what their site says,

    * Fix partition table, recover deleted partition
    * Recover FAT32 boot sector from its backup
    * Rebuild FAT12/FAT16/FAT32 boot sector
    * Fix FAT tables
    * Rebuild NTFS boot sector
    * Recover NTFS boot sector from its backup
    * Fix MFT using MFT mirror
    * Locate ext2/ext3 Backup SuperBlock
    * Undelete files from FAT, NTFS and ext2 filesystem
    * Copy files from deleted FAT, NTFS and ext2/ext3 partitions.

Technically you can recover all your lost data if only if you have not written over the recovering data.

To know more about TestDisk visit their site: http://www.cgsecurity.org/wiki/TestDisk

Step by step tutorial of TestDisk http://www.cgsecurity.org/wiki/TestDisk_Step_By_Step