Have you accidentally deleted a file? Has someone deleted a file/folder from your computer on purpose? Have you saved important files on a CD/DVD or some other data carrier which your system does not recognize due to some physical injury? Has the power run out while you were working on your computer and now your system does no longer start up?
Most of the files are restorable. Give us a call or send us an e-mail to firstname.lastname@example.org if you need any additional information.