Virtual memory is storage space on your computer’s hard disk that Windows uses in conjunction with random access memory (RAM). All programs run in system should be operated by memory. If the program running occupy too large or too many memory, it will leads to the memory exhausted, and if the windows lacks the RAM to run a program or operation, the windows will take virtual memory to compensate.
If you receive warnings that your virtual memory is low, you'll need to increase the minimum size of your paging file. When you install system, windows will set the initial minimum size of the paging file equal to the amount of physical RAM, while the maximum size of the paging file equal to three times the amount of physical RAM. To increase the size of virtual memory to stop windows popping up the message, you should change the size of virtual memory.
In windows XP:
1 Click Start and then click Control Panel;
2 Click Performance and Maintenance, and then click System;
3 On the Advanced tab, under Performance, click Settings;
4 On the Advanced tab, under Virtual memory, click Change;
5 Under Drive [Volume Label] click the drive that contains the paging file that you want to change;
6 Under Paging file size for selected drive, click to Custom size check box. You can enter the amount of memory you would like to reserve for Virtual memory by entering the initial and maximum size.
7 Click Set
In windows 7:
1 Right-click my computer, clicking Properties;
2 In the left pane, click advanced system settings,
3 On the Advanced tab, under Performance, click Settings.
4 Click the Advanced tab, and then, under Virtual memory, click Change.
5 Clear the automatically manage paging file size for all drives check box.
6 Under Drive [Volume Label], click the drive that contains the paging file you want to change.
7 Click Custom size, type a new size in megabytes in the Initial size (MB) or Maximum size (MB) box, click Set, and then click OK.
In some degree, Virtual memory can help you to increase the speed of the computer reading data when the computer is lack of RAM.