Win2000 (the entire NT line) is a virtual memory Operating System
which uses 'paging' to provide memory resources to applications.
Paging allows data, not immediately needed, to be saved to disk and
returned to the application when needed -- it also allows unnecessary
code from executables and DLLs to be discarded and retrieved again
from the executable file when (if) needed.
[Note: Paging and "swapping" are not generally synonymous. The
WinNT family uses "paging" rather than application swapping.]