System Report
1. Click 'Start,' then 'Control Panel.'
2. Choose 'Performance Information and Tools.'

3. In Windows Vista, click on 'Advanced Tools.' Choose the 'System Health Report' option and allow the test to run. In Windows 7, click 'Rate This Computer.'
4. Read the report to detect potential problems with your computer's hardware.
POST Error Codes
5. Shut down your computer and allow it to rest for 30 seconds
6. Power on the computer.
7. Listen to the number of beeps that sound from your speakers when your computer runs POST. According to the Indiana University IT department, POST is a hardware diagnostic utility that runs as soon the system powers on. It tests your RAM, video card, motherboard, and keyboard controller, among other hardware components. The number of beeps you hear indicates a hardware error. A single beep usually indicates a normal boot.
Mac Apple Hardware Test
8. To test hardware on a Macintosh computer, install the Apple Hardware Test disc.
9. Restart your computer and hold the 'C' key.
10. When the Hardware Test comes up, release the key and allow the test to load. Click 'Extended Test.'
11. If you experience intermittent hardware issues, you can press 'Control-L' before starting the test. This will toggle the loop switch. According to the website 'X Lab,' you should run loop tests overnight to detect RAM issues. End the loop by pressing 'Command.'