I've always vigilantly backed up all my data and have rarely lost a file. Most people don't do this. Most people just use a computer until it crashes or gets trashed by viruses and then panic. That's why an entire data recovery industry exists. I'm thinking of applying for jobs at such companies. I already work for a company that decontaminates computers from malware. If I were to recover data from a computer whose operating system had crashed or where someone had inadvertently deleted a bunch of files, I imagine I could remove the hard drive and put it in a casing (turning it into an external drive) and then run file recovery software on another PC. That way no files would be overwritten via the installation of such software. Otherwise, perhaps there are portable versions of data recovery software that you can run from a thumb drive. I wonder what other techniques such companies use, such as when a digital camera card crashes or a hard drive straight up crashes. I want to polish up my skills so that I can truthfully put them on a resume. I'm thinking of getting a no cheap OS PC and then putting different Windows on it and deliberately deleting s**t or virus trashing it just for the purpose of practicing data recovery.
for computer forensics there are many tools at ones disposal for the right amount of cash... some of the most advanced things i've seen are forensic dongles that plug into usb drives so that one does not have to remove the drive from the machine at all. these are completely portable and universal from what i understand and give the user more options than simple data recovery software that is found online... EnCase is one of the better known that i'm familiar with. you should check it out. and as acrsn said, good luck