(Or "WIN386.SWP") 386SPART.PAR is a hidden file created by Windows 3.1 for use as virtual memory swap file. It is generally found in the root directory, however it may appear elsewhere (typically in the WINDOWS directory). Its size depends on how much virtual memory you have set up under (Control Panel) Enhanced under Virtual Memory. If you move or delete this file Windows will complain the next time you start it with a Swap File error.
Windows 95 uses a similar file, except it is named WIN386.SWP, and the controls for it are located under Control Panel - System - Performance tab - Virtual Memory.