Some people are "Window happy" and like to have more than 5 windows or applications

 open at one time. As they soon find out, this practice tends to crash a system on a

regular basis depending on the type of computer and program.

It's generally a good idea not to have more than 4 memory-intensive programs

 open at the same time, unless you have a very good computer.

But if you insist on tempting the Fates, you can monitor your system's resources

with the Resource Meter. So, you can close a window or two when the resources

 start to get dangerously low.