Computer security Question:

It can. Memory pages are swapped or paged to disk when an application needs physical memory. Even though the page file (see Control Panel->System->Performance->Virtual Memory) is not accessible while the system is running, it can be accessed by, for example, booting another OS.

There is a registry key that can be created so that the memory manager clears the page file when the system goes down:

HKLMSYSTEMCurrentControlSetControlSession ManagerMemoryManagementClearPageFileAtShutdown: 1

Note that the clearing of the page file only is done when the system is brought down in a controlled fashion. If the machine is just switched off or brought down in any other brute way, of course no clearing will be performed.