Windows "Delete" doesn't delete, it only sends them to the Recycle Bin, they won't get overwritten unless a second = definite delete is made. They can be brought back easily, by opening the Recycle Bin, found in Windows Explorer \ Desktop... Open the Bin, right click any file and choose "Restore" - or choose several files, and get them all restored.
Like landerio notes, the main first caution is not to write anything new on the disk. If you have truly erased, I've used Recuva, works fine, and the best would be to get the portable version, through a friend or something. Put it on a flash drive, that way you need nothing done on your own disk, http://www.piriform.com/recuva/features/portable-version