Go to the Control Panel
Administrative Tools
Local Security Policy
Local Policies
Click on Security Options
Right hand menu - right click on "Shutdown: Clear Virtual Memory Pagefile"
Select "Enable"
Reboot
For regedit users.....
If you want to clear the page file on each shutdown:
Start Regedit
Go to HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerMemory ManagementClearPageFileAtShutdown
Set the value to 1