Virtual memory is used when real memory does not suffice to run all active tasks. The system 'pages out' the lowest priority task in order to make room for the higher priority task. The page-out is in 4K blocks and goes to the virtual memory (page file) which is allocated on the system disk/partition. In windows 7, this is the procedure to change the virtual memory/page file size. You find that in the Help and Support section when you type 'pagefile' (without quotes) into the start/search box.
Click to open System.
In the left pane, click Advanced system settings. If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
On the Advanced tab, under Performance, click Settings.
Click the Advanced tab, and then, under Virtual memory, click Change.
Clear the Automatically manage paging file size for all drives check box.
Under Drive [Volume Label], click the drive that contains the paging file you want to change.
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.