1. Get Rid of Dust
One of the most common causes of overheating is dust and dirt. So you need to keep your system clean, inside and out. Try to clean it once a year using lint-free wipes. Make sure you use an antistatic wrist strap as well to protect your system when cleaning inside the case.
2. Get Power Protection
One of the saddest things in many PCs is that they are not surge protected. Surge protectors are a good investment - they protect your PC from that unfortunate power outage or lightning strike. Try to get one that has a warning indicator and is UL 1449 certified.
3. Turn Off the Monitor
One tip I always apply at home - turn off the PC monitor when its not in use. I treat the computer monitor like a TV - don't waste your monitor's power if you're not using it. This is especially important in LCD monitors, which may burn out or get bad pixels after long periods of use.
4. Keep the PC Running
Many people don't realize that its harmful to power up your computer from a cold state. This is especially true when done repeatedly within a short timeframe. Try to leave your PC running as long as possible - or use the Microsoft Windows' Power Management settings to put your machine into hibernation rather than completely shutting down.
5. Hard Drive Health Check
If you use Windows XP, you should regularly check your hard disk's health with an error-checking utility.