Go to :-
Basically it is :-
Some third-party programs can temporarily store unencrypted (plain-text) passwords or other sensitive information in memory. Because of the Windows virtual memory architecture, this information can be present in the paging file.
Although clearing the paging file is not a suitable substitute for physical security of a computer, you might want to do this to increase the security of data on a computer while Windows is not running.
There is a tiny automatic program as described in the link, but to do this yourself :-
Start Registry Editor (Regedt32.exe).
Change the data value of the ClearPageFileAtShutdown value in the following registry key to a value of 1:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management
If the value does not exist, add the following value:
Value Name: ClearPageFileAtShutdown
Value Type: REG_DWORD
This change does not take effect until you restart the computer.
It works perfectly and there is no problem stepping down the Registry Editor listing to find the keyword and insert "1".