Click the blue/gray finder face icon in the bottom left. Click the house on the left hand side (if there isn't a house showing, click Go up at the top then Home).
Double click the Library folder
Grab the Caches folder and drag it to the trash.
Click Go at the top of the screen then click Utilities. Double-click Disk Utility. Click your hard-drive (probably called Macintosh HD) then click (once) on repair disk permissions. When that's done, quit disk utility and shut down the computer.
Locate the Apple key, Option key, P key and R key. Turn it on and hold down those 4 keys until you hear the startup chime 3 times then let them go. Once it boots up empty the trash.
If you have an older mac (G5, G4, G3)... The next step won't work on an Intel Mac
locate the Apple key, Option key, O key and F key. Turn it on and hold down those 4 keys until you get to an all-text screen then let them go. Type in the following commands (no spaces in any of them)
set-defaults
reset-nvram
reset-all
Once it starts up empty the trash.
And finally, if you want to check your Operating System... there's 2 ways to do that. (Both of them work on Intel or G5, G4, G3).
a) if you have the discs:
Put install disc 1 in the computer. Shut the computer down. When you turn the computer on (as soon as you can after releasing the power button), hold down the letter C until you see the grey apple with the spinning gear underneath.
You'll get to a screen that says "choose english as the main language". Continue to the next screen and look at the very top of your screen. Click Utilities (next to Finder) then click Disk Utility. (If you don't see Utilities, try clicking Installer then Disk Utility). Click your hard drive then click Repair Disk. Do NOT do repair disk permissions from the disk!
Once that's done, click Disk Utility, quit. Then click Installer, Quit Installer then Restart.
b) if you don't have the discs:
Get the computer to shut down. When you turn it on, hold down the apple key and the letter S. When you get to an all-text screen release the keys. Type in
/sbin/fsck -fy
(please notice the space between k and -)
That will check your operating system. You're going to get one of 3 things
i) the volume <name> appears to be okay (congrats you're good to go!)
ii) one HFS volume repaired (press the up arrow and run the command again, it fixed something).
iii) the underlying task reported failure on exit (your HFS volume is pooched, you'll likely need to do erase & install or use a program like Disk Warrior).
iv) One HFS volume repaired, one volume could not be repaired (same as iii)
Once it's all done, hold the power button for 5 seconds to get it to shut down then turn it on normally.
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