Unused memory cleaning

When i’m running my .exe, a strange thing happens. When i look at the Task Manager, my process is taking around 8MB memory. I have this tool( SpyGuru ) that reduces that space to 1.2MB of used memory. I think this is unused memory and if the OS needs it, it?s going to take it, but i would like to know how SpyGuru does it. I have already tryed to use IMalloc::HeapMinimize, _heapmin and HeapCompact( with all thred heap handles ). Notice also that my process has some threads running and i’m under Win2000

Thanks in advance,
Miguel Tadeu