Mac Hardware

The Macintosh computer's hardware includes items such as the keyboard, mouse, monitor, and actual computer (or CPU). If you are having trouble with your Mac's hardware and not the software, it's a good idea to try to isolate which piece of hardware might be causing the problem.
For example, if your mouse and keyboard are not working, then make sure that the keyboard cable is firmly plugged into the keyboard and the computer. If your printer is not working, be sure that all the printer cables are plugged in correctly. Unless you are using USB cables, turn off your Mac before unplugging and plugging in its cables.

Dead internal battery

A common hardware problem is having the internal battery of your Macintosh fail. One symptom of a dead or failing battery is if your Macintosh's clock is always off. If the time shown in the upper right hand corner of your screen is incorrect, then reset the time.
Mac OS 9.x
Go to the Apple menu and select Control Panels, then select Date & Time.
Change the time to the correct time and shutdown your computer.
Mac OS X
Go to the Apple menu and select System Preferences.
Click on Date & Time.
Change the time to the correct time and shutdown your computer.
If your Mac clock is wrong when you turn on your computer, the most likely is that the internal battery needs to be replaced. Other symptoms of a failing battery are failure to retain Chooser (printer) settings or difficulty in turning on the computer (the monitor doesn't come on).

Mac - Chimes of death

The “chimes of death” or a sad Mac can indicate a hardware problem. According to Apple, the "chimes of death" are a series of four to eight tones that are sometimes heard immediately after the normal start-up chime, after which you get a disk with a blinking question mark. On a PowerMac, the sound will be a 'car crashing'.
If you have just installed RAM into your computer and hear the "chimes of death" then double check that your RAM was installed properly, specifically that you have the right type of chip for your model, and that the chips are seated firmly.
Otherwise, try starting your Macintosh with extensions off (restart and hold down the shift key until you see "Extensions off" or "Extensions disabled") message. If your Macintosh will start, then one of your extensions is causing the problem. If it will not start, then try starting your Macintosh from a bootable diskette or CD. If your Macintosh now start's, you should perform a clean install of your system software.
For more information and troubleshooting, see this Apple article:
You hear "breaking glass" or musical beeps" (outside this site)when you startup your Mac.