|As mentioned, data recovery services are very expensive. Look for local listings or Google with the words Data Recovery and your country and nearest major city.|
Always keep a current back up. If the data is EXTREMELY important then use a RAID 1 or 5 disk array AND keep an onsite back up (in a fireproof safe) and an off site back up (reputable back up service or take home portable hard drive) and (that's AND, not OR) possibly even DVD-r disks (if the files are not too large) for at least triple redundant protection. NEVER trust one source only for important information.
You have to be a little bit crazy to keep you from going insane.