you may get some conflicting opinions on this one:
my advice is just to let windows manage it.you have 1 gig of installed physical ram so there should be no problems here with this ammount of installe ram with most tasks what so ever if you choose this option.
some people say the ideal setting should be around one and a half to two times your installed ram in both the min and max value boxes.this stops windows from resizing the swap file when it needs to.with your ammoun of ram installed and set to system managed size it shouldnt happen often if at all.
i have only 512mb of installed ram,i play latest games,edit video,photo etc and have tried various different settings for the xp swap file and can see no difference at all in performance when setting to either a fixed size,windows managed size or even running with no swap file at all.
if you had a low ammount of installed ram then it may be a different story altogether.
try various settings and see for yourself but as above i would just let the system handle it.