
The trick is that once new information is written to the hard drive, deleted files (actually, ones marked for deletion) can be overwritten without your knowledge. So, in fact, the absolute #1 rule for recovering a deleted file is:
STOP using the PC right NOW!
The less you touch the filesystem, the greater your chances of recovering a deleted file successfully. Another thing that you should avoid is defragging (defragmentating) the HD. This also runs a good chance of losing deleted files irrecoverably, as data are reshuffled physically on the HD by this process.
Continue read here
Recover Deleted Files in Windows - The 1 Fatal Mistake to Avoid