You have discovered that your system won't start because the data on your drive has been scrambled, can it be recovered?
With all the data on the drive being scrambled, it would be nearly impossible to find what and how it got on the system, there are 10s of thousands of viruses and 500 times more malicious software that can attack and cripple your system, in many case totally destroying data beyond recovery. Getting a virus is only a matter of odds, if all your software updates are in place and your internet security is working you can still get bad things on your system simply by being redirected to another site of lesser reputability. There is no silver bullet when it comes to protecting your system, it's more a matter of keeping everything working and updated and also how you use the web can influence your system stability.
Having regular updates on all your software along with clean backups will provide your assurance of retaining your data in case of catastrophic failure.
Don't rely on the myth that data can always be recovered off your disk.