Even though you have multiple gigabytes of physical memory (RAM modules), Windows operating system, especially Windows Vista and Windows 7 is always hungry for more memory. And virtual memory is the free and easy resolution, by using a paging file stored on hard disk which can be used as if it’s RAM. However, virtual memory’s paging file, i.e. pagefle.sys with system and hidden attributes, takes up hard disk drive space.

On dual-boot or multi-boot system running multiple instances of Windows operating system on different hard disk drive (partition or volume), there will be multiple copy of pagefile.sys created and existed on all system drive. On PC computer running low on drive space, multiple pagefile.sys files will waste more disk space, as normally each pagefile.sys has the size of 1 GB or more, sometimes more than 4 GB, depending on physical RAM installed. Similar situation can also happen on virtual machines, where each virtual hard disk gets unnecessary bigger due to own paging file (However, it’s unlikely more than 1 virtual machine can run at the same time if using same page file).

In order to avoid wastage of disk space to VM paging file, there is workaround that instructs Windows XP, Windows Vista, Windows 7, Windows Server 2003 and Windows Server 2008 to use the same single paging file. The hack allows pagefile.sys to be shared among all installed instance of the operating system, as long as the OS can ‘see’ and access the pagefile.sys and filesystem on antoher HDD partition or volume that meant for another OS.

In order use only a single pagefile.sys for all Windows operating systems installed on the PC, user first has to decide which drive to place the pagefile.sys. The drive can be existing system drive for an operating system (which means no chance is required for the installed OS), or a new formatted partition or drive.

Once determined which drive to place the pagefile.sys, the partition volume must be visible to the each and every system to share the paging file. If the partition is not visible, add in the disk or assign drive letter using Disk Management in Computer Management of Control Panel. Next, determine the drive letter path of the drive.

To switch and change the system’s paging file to use the shared pagefile.sys, right click on Computer, and select Properties. Then click on Advanced system settings (in Windows XP and Windows Server 2003, go to Advanced tab). Click on the Settings button in the Performance section, then go to Advanced tab. Under the Virtual memory section, click on Change button. Uncheck the option of Automatically manage paging file size for all drives. For all drives that you don’t want pagefile.sys to exist, select them and then set as No paging file to disable paging file storage on the drive. For the drive that contains the shared pagefile.sys, set it as Custom size (and enter the value for initial size and maximum size), or System managed size.

Repeat the process for each operating system installed. Remember that the drive letter for pagefile.sys may be different for different booted OS, especially when user installs each operating system on different partition.

Tip: If the pagefile.sys (hidden by default) still exists on drive not with the shared pagefile.sys after the trick, delete the file away.