How to improve battery on a laptop running XP?

If somebody has any useful tips, please – do tell! :) Since I got my new Intel T2400 CPU powered laptop, I can’t get more than 2 hours of battery work time with it. The laptop brand is Compal (yes yes…I know) and it doesn’t come with auto screen dim power settings in BIOS. I would really like to know why XP doesn’t have that pretty OS X feature which dimms the screen on laptop automatically when you are not working (power saving options). I couldn’t find 3rd party implementation of this aether.
I tested SpeedswitchXP, little utility that switches processor speed – my best guess is – it doesn’t do squat. Since Intel already introduced this into mobile cpu’s. I tested some shitty 1996 battery extender apps – no luck. One thing I find very annoying is the laptop screen dimmer built into XP. I have no idea why it does not remembers my settings.

Example – I am on AC power and I set screen brightness to maximum. Then I unplug AC power and dimmer doesn’t apply minimum brightness settings. When I apply it manually (FN+F4), and swtich to AC power, screen undimms, then I disconnect AC, screen goes to low brightness. After standby or hibernation settings are forgot. When I go to battery power, screen does not dimm it self.