First of all try closing some unwanted applications, and see if that helps. The message is displayed when there is no sufficient memory on the PC or the virtual memory settings are not set high enough.

The best option in most cases is to let the operating systems manage the size of your virtual memory.

If you have Windows XP on your machine you can check if that is the case:
Start -> Control Panle -> System -> Advanced -> Performance -> Settings -> Advanced -> Virtual Memory -> Change —-> make sure that the “System managed size” option is selected