This depends on how did you delete the files. If you deleted them via Recycle Bin, then emptied the recycle bin, they may still be recoverable (although we would lose their name, but not extension). Look in the recycler dir's (of all drives) for files with the expected extension and last access time. This also depends on how much writing operations were perfomed on the drive. If there were a lot of activities, there is a chance that your files have been overwritten by other data and became non-recoverable now.