after I made my last computer upgrade I did not bother to return the side panel of the computer case and consequently I hear more noises, from the inside of my computer, than would be possible were the case closed. I am starting to hear the system hard drive (the one with the operating system on it) start to get occasionally more noisy than seems regular. Does this mean it is not long for this world and I should think about upgrading it before it brings my entire computer down or could I have quite a bit more life in it. What do you think.
More about :system hard drive occasionally noisy failing
If it's more of a chittering noise than a clunking or grinding noise, it should be fine. If it sounds like a clock with a "tick" every second, then it might be on the way out.
Leaving the side panel removed is often not recommended as it disrupts system air flow and makes it easier for foreign objects to break things. The panel also provides a certain level of noise dampening, as you may have already discovered.