Every PC user has a computer problem now and then. Even the most stable, secure machine is not safe from buggy software, failing hardware, or even the occasional loose wire. PC problems can be a huge headache, bringing productivity to a halt and potentially costing you money. Here are some of the most common computer problems, and their possible causes.

The Computer Won't Turn On

This can be a computer user's worst nightmare. You hit the power button and nothing happens. Any number of things can cause this computer problem — it may be something as simple as a loose cord, or as serious as a dead power supply.

Another common PC problem is when the computer turns on and the fan and lights come on, but the machine doesn't boot, or shows a blank screen. This could be anything from a dead (or unplugged) monitor to a dead hard drive or corrupted boot sector.

Lockups and Freezes

The infamous "blue screen of death" has frustrated many a user, as it brings the computer to a halt and displays an error message that's utterly indecipherable to most computer users. Lockups can be caused by any number of issues — sometimes it's buggy software, or a system running out of memory.

Sometimes it's a bad hardware driver causing the issue. More seriously, it can be a sign of overheating, RAM going bad, or the hard drive failing. Components get loose inside the machine and can also cause computer errors, sudden lockups, or even spontaneous shutdowns.

Slow Performance

When you delete files and applications from the computer, all kinds of junk can get left behind. Useless files and data can accumulate and degrade system performance. Ironically, antivirus and anti-malware software, while vital to the health of a computer, can slow down a PC's performance. Low hard drive space or not enough RAM in the machine can also cause computer errors and slow down the machine.

Strange Noises

Is your machine making a strange whirring noise? It might be a fan dying. Computers accumulate dust over time, and when fans get clogged, they can slow down, decreasing their effectiveness and making an unpleasant grinding sound.

Another common computer problem is the dreaded "click" of a dying hard drive — one of the most potentially destructive PC problems there is. If you hear a rapid clicking or clunking noise inside your computer, it's best to get a backup plan in place, if you don't already have one — chances are your hard drive is close to dying and taking all your valuable data with it.