I'm amazed at the number of posts that appear on a regular basis bemoaning the fact that the poster has lost this, that or the other disk or product key that is vital to the operation of their computer - by that I mean the disk containing the copy of the operating system (whether a full copy or a recovery disk), a vital software disk and so on.
Remember that all of these disks and their passwords/keys are valuable and essential if something goes wrong or just packs up.
Keep the disks and activation keys of all installed programs, hardware drivers and especially operating systems in a SAFE PLACE where you know for certain that you will be able to find them again. It will save a lot of heartache and fruitless searching when the inevitable happens.
Not specifically but this comes up so often and I appreciate what a problem it can cause people so it's a bit of advice to try and help anyone who may come into that situation. I'm not "having a go" at you or anything like that.
In the same way that, as stalion says, people think their machines can't crash or that their hard drive can't fail or any one of loads of other disasters that might befall your computer can't happen. Well, it can happen and it does happen.
If you have never been let down by your computer, you are very lucky and you can guarantee that you will be one day.
I took care of my disks on my ls120 floppy drive i.e. 120 mb disks but the drive itself has packed up. Whilst pressing the button to remove a disk the button itself broke away and probably a small tip of a thingy inside so system throws out any floppy on start up. I tried to get another drive but the drive or superdrive is no longer available or marketable. However by some luck of the draw I managed to get someone who has a drive unused still in its original packing whether it is true or I'll get it is another matter!!
As well as taking care of your original driver/OS discs etc, make copies of them. Store the originals somewhere really safe, and use the copies for day to day use etc. CD's are not as indestructible as they were flaunted to be on Tomorrow's World back in the day!