Whilst I completely sympathise with the potential loss of valuable data, I cannot agree with the above statement. Sorry to be blunt, but relying solely on a hard drive to store your valuable data is a fools game - I have to fix peoples computers all the time and time and again they don't have any sort of backup. Hard drives fail all the time, they are not designed to last forever so you cannot rely on them unfortunately.
However, your data maybe retrievable but that depends on the O/S and reading it, the first step will be to remove the hard drive and try it in another machine if you can? If you take it out or take a picture of it, I reckon you should get some help from us geeks and if we can get you going again, we will