If you REALLY need the files back, bring your machine to any small computer shop and they should be able to recover your data. The only way to permanently delete anything off a harddrive is to either destroy the disks completely or through a complex process that takes a few hours per item deleted. Just to warn you though, data recovery takes time and can be quite expensive. Definately a last ditch resort sort of thing, but it works 99% of the time.