Almost lost my hard drive

I don’t know what happened to my hard drive, but it wasn’t being detected a few hours ago. I tried to boot into Windows, but I had no such luck. I was running Knoppix 3.3 off a CD for a bit, thinking I was doomed. I had some data on that hard drive that I haven’t burned onto CDs yet. (I do have another hard drive in my system, split into two partitions in case my primary one fails. However, it only runs at 5400 rpm.) Luckily, I got home after coaching, and found upon trying again that it was just fine. I ran both standard and advanced IBM Fitness Tests, and both checked out okay. My question to you is…what am I supposed to do if nothing shows up like that?