Yeah, stay away from so called optimizing software, and the registry cleaners and all that nonsense. Its not nearly smart enough to adequately do the job.
There are two types of people in this world, people who have lost data, and people who will. I wouldnít kick yourself around too much about it. Chances are your hard drive would have crashed at some point down the road without you having done anything. On the plus side, you now know that you should maybe burn a CD or two ever month. I tell all my customers to keep there data in two places, and the important data in three. By far I would say CD/DVD is the best form of data backup. Hard drives fail, its in there nature. Itís a metal disc spinning at 7,200RPM. Thatís a bad design. CDís and DVDís are a piece of plastic with a reflective sticker on it. No moving parts, and a virtually limitless shelf life. Floppyís and zipís and tapes all have moving parts and they are all susceptible to mechanical failure from being dropped and such.