How to Fix a Mac OS Crash

Press 'Command-Option-Esc' at the same time. The Force Quit Applications window opens, displaying all of the open applications, with 'Not Responding' beside the application that caused the Mac to freeze. If this window does not open, press 'Command-Option-Shift-Esc' for three seconds to force quit the unresponsive program. Then open the Force Quit Applications window.
Click any application that says 'Not Responding' and click 'Force Quit.'
Restart your computer if you have not shut it down in more than 24 hours. This will clear memory being held by any troublesome applications.
Click the 'Finder' in the Dock to open a new Finder window. Click 'Applications,' then the 'Utilities' folder. Double-click 'Activity Monitor.' This will show you what resources are being used by processes and applications.
Click the '%CPU' tab to sort this column. Processes and applications are now sorted in descending order. Processes using most of the Mac's CPU (Central Processing Unit) will be shown first.
Click the 'Real Memory' tab to see which processes and applications are using the most memory. Do the same for 'Virtual Memory.' Real memory is stored on the memory chips, while virtual memory is stored on the hard drive.
Close any application that is using an unusual amount of memory or percentage of the CPU. What is unusual for memory usage will depend on the programs you run, but anything over 700MB should be examined. Any process using more than 20 percent of the CPU for more than a second or two should be considered unusual.
Relaunch the application that caused the Mac to crash.
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How to Determine If You Need More RAM in Your Computer

Eliminate any problems that could be causing effects that you may mistakenly blame on a lack of RAM. Use measures such as scanning your computer for viruses, defragmenting your hard drive and making sure at least 10 percent of the capacity on your hard drive is unused.
Look out for specific problems that may result from not having enough RAM. The main one is applications running slowly and being unresponsive. Less common ones include parts of the display on your screen appearing to be missing, or on-screen messages explicitly referring to a lack of memory.
Keep track of the problems you experience over the course of several days, noting which applications you are running. If the issue is related to a lack of RAM, the problems should happen regularly and not necessarily be affected by the particular application you are running.
Check how much RAM your computer uses. Open and run a typical combination of applications that you would normally be running at the same time. Then open Windows Task Manager by clicking the Start button (the Windows logo at the bottom left of the screen), typing 'task manager' and pressing the Enter key. In Task Manager, keep an eye on the figure next to 'Physical Memory' while carrying out a range of typical tasks in the applications you have open. If the listed figure is consistently at or close to 100 percent of memory, you may benefit from added RAM.
Check whether your operating system is 32-bit or 64-bit by clicking the Start button, then clicking 'System and Security' then 'System.' Look for the details next to 'System type.' If you have a 32-bit system, you will not get any benefit from having more than 4 GB of RAM.
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