With this option you can change your computers RAM availability without buying any more Ram sticks or something like that. This very well works with my windows 7. I dont know anything about it in any other OS.To do this first go to start. Go to control Panel and Select the option "System and Security" from it.
In it there will be several options. Select the option called system from it. In the next page you will see many options. In the left side of the page you can see some options. Choose the option Advanced system settings. See the figure below. An box like this one below appears. See all the options in it cause it might be useful to you if you want to change any of these settings later, its very useful. Take the advanced tab.
Select the settings option below performance option and anathor box appears. In this tab take the advanced tab and you will find the options to change the settings here. The image is given in the right. Below virtual memory category select the box with change written on it.
Now a new box appears. the box is given below. Unselect the box "Automatically manage paging file size for all drives"
Now select the custom size option and you can select the minimum and maximum values which you have to give.
By default the maximum size is 3 times of original ram. After giving values click the button set.You will now have RAM increased.
All done!!