I particularly recommend today's Giveaway of the Day (see bottom of the sidebar). HDDLife Pro monitors the condition of your hard disk and warns you if there is any problem. You should get ample warning if your hard-disk is in danger of failing.
It couldn't be simpler to install. All you need to do is download it and run it once - and that's it. You will have continuous monitoring from then on.
Even if you miss the free giveaway expiry - it's still well worth buying. If you read this later than today, you can still click on the link and the program will be available to buy at the manufacturer's normal price of $29.
Remember these giveaways are not Shareware, and do not expire after 30 days or any other period. They are full programs which are free as long as you download and activate them on the day they are offered.