When it comes to an uncommon noise inside your computer, you want to fix it sooner, not later. A clicking sound is almost always a sign of malfunction. Most clicking parts can be easily replaced – such as a fan or hard drive – but if left untreated, broken parts can damage more of your computer.
Back Up Your Files
When your computer begins to make an unexpected noise, back up your files – all of them, immediately. Even if the clicking noise turns out to be noncritical and easily repaired, its better to be prepared in the event of total computer malfunction. Once you've saved copies of all your important files, go forward with identifying and repairing the problem.
Your computer is full of fans to dissipate heat inside the computer – a fan over your processor, a fan on your graphics card, even a fan or two to blow all that hot air out of the back of your computer. This sort of clicking may be caused if the fan is clogged and can't turn properly – or if a fan blade is broken. Check that the vents aren't obscured in any way, then use a can of compressed air to blow any debris and dust out of the fan itself. If you feel comfortable doing so, you can replace fans from home.
If the source of the clicking is your hard drive, start saving up for a new hard drive immediately. A standard hard disk drive is filled with spinning platters and moving heads that read and write data on the platters. It is a precise machine; when it begins to click, it means that pieces are moving out of alignment. This is sometimes due to age – all hard drives will eventually fail over time – or due to some physical trauma, such as your computer being dropped on the ground.
The optical drive on your computer may spin up during the boot process, as most BIOS systems are set to boot from CD first and HDD second. If your optical drive is clicking when you try to access it, something may be stuck inside the drive. If the drive does not open, it may be jammed or broken beyond repair.
The power supply has its own fan – and like the fans in the computer, it can become obstructed and cause noise. Using compressed air, clean the power supply fans to remove any obstructions or dust from the power supply. If it continues to click after you've cleared it out, take your computer to a professional. You may need to replace the power supply.