Virtual memory is a part of the hard disk that Windows uses like extra memory. Ifthis message appears in Windows XP, check that it is being managed properly.
Virtual memory, also known as a page file or swap file, is a file on your hard drive (C:\pagefile.sys by default) that Windows and applications use in addition to physical memory (RAM) as needed. The default and recommended size of this file is 1.5 times the amount of physical memory. Virtual memory is the sum of physical memory and the page file. So if your computer has 512 MB RAM, it will have a 768 MB page file by default, for a total of 1.25 GB of physical + virtual memory
To determine which application is causing this problem.Press Ctrl+Alt+Del to access Windows Task Manager. Navigate to Processes tab. Here you can see the list of all the processes running in your system.Click View, Select Columns
Now you can check the Virtual Memory usage in your Processes tab. Click the top of the VM Size column to arrange the processes by their VM Size from largest to smallest.
Every application will use more memory the longer you keep it open. This is one reason that Windows becomes more and more unresponsive the longer you keep it running, and why you end up eeding to restart your computer periodically.