Memory Mangement Problem in 5.1-RELEASE

Hi,
I have 160Mb of SDRAM (PC100) on a 233Mhz CyrixInstead machine and I
seem to have memory mangament problems. The BIOS indicates I have 160,
so does the BSD bootstrap program. 

When I launch GNOME 2.2 everythings is good as gold untill I open the
System monitor program. It says that I have 149 Mb of RAM which is fine
( 4Mb of video..and the rest...god knows).

I open every program I have and after 107Mb the machine starts to swap
with about 50Mb left unused!!

I recompliled the GENERIC kernal for the sake of it really (Im still an
amature) I didn't mess with the configuration files or anything (I just
don't know how!!).

Is this normal or mismanagement of memory in the 5.1 version of the
excellent FreeBSD kernel??