do not load textures in memory
get fsautostart - it will help you shut down anything not necessary to run
make sure anti-virus shuts down
turn off screen saver
remove as many icons on desktop that you can- use blank background
use game default sounds
after you start game - tab out back to windows desktop- start task manager see what is still running and end process of what you can
run game at 256 or 128
after that - still not working - you are in need of a new system...
good luck