When u delete a file from an operating system, the electronic
data of the file itself is not removed from the hardisk. It's just
that the OS file system is not pointing to that file anymore. This
applies even to reformatting.
When Windows tell you that if you click OK, all data will be lost,
that's bullshit for computer n00bs.
But overwriting data is sure-bye-bye.
Go download TuneUp Uilities at www.download.com. It has a recovery
utility which allows you to recover most of your files even ones
deleted from reformatting.