The files are probably still there: the space is marked as free for over-writing. You want to install and use an un-delete utility. There are a couple freeware ones I've seen reasonably decent things about:

Undelete Plus http://www.undelete-plus.com/

Runtime Get Data Back http://www.runtime.org/data-recovery-software.htm (looks like you might have to purchase a key to make the recovery permanent)

FreeUndelete http://www.officerecovery.com/freeundelete/