Halo 2 graphic problems,,particles not visible properly

hi friends,, this problem is bugging me for quite sometime ,I have
intel e4500 2.2
intel 945 gcnl
2gb ram
nvidia 9600 gt (59watts)
vista home premium (32-bit)
[running on 1024x768]
as far as i know i have enough specs to run halo 2,but my problem is i do not get some particles with everything maxed
-electricity lines on energy sword & no light while switching onto it
-sometimes smoke is not visible like from gravemind's mouth in cutscene
-teleportation rings on masterchief(gravemind cutscene)& arbiter(uprising cutscene) .....i have noticed only this few problems,,BUT SOMETIMES THEY DO APPEAR,, otherwise the game runs fine everything lookS good only these things are problematic i have tried installing different copies of halo 2 but all are the same , i updated all my drivers..i installed the directx from microsoft (directx websetup version 9.26.xx)[should i be updating the direct x on vista]
OKAY ALL I WANT IS ,DO SOMEONE KNOW Y IM EXPERIENCING THIS PROBLEM IN HALO 2 WHATS CAUSING IT,,AND DO SOMEONE HAVE THE SAME PROBLEM???