I'm trying to get above 4+ hours battery life on my laptop.
As it stands, I can only get 2 hours worth of battery life on power saver mode*. Though windows vista serves me well for my gaming purposes, I would like to consider trying to dual boot with a linux distro so I can use my laptop as a long life word processor.

This distro** would have to boot into a mode that should use 25% of my cpu at maximum***, and at most, 512 MB RAM. Under these settings, it should smoothly be able to use abi word, and browse the internet via firefox at the same time.

Now the my two questions, how would I go about doing that, and would it achieve 4 hours of battery life , plus the above criteria?
Please Help.

My laptop:
Gateway M-6827.

My Specs:
Gateway Official Site: Products - M-6827 Pacific Blue, Notebooks, Product Details
2.00 GHz Intel Core 2 Duo
3 GB DDR 2 RAM
Intel X3100 with 348 VRAM
15.4 in screen
1920x 1280 resolution (in vista)

*50% CPU, 6x Multiplier.
** I'm thinking Damn Small Linux or something fast like that.
***does that make a difference? my multipliers only go down to 6x

Doubling the battery life with only a software change would be a drastic change, I don't believe it would be possible, getting 20-30 minutes extra over Windows is about as good as I've been able to do.

The best you can do is set processor scaling to the minimum speed, dim the screen as much as possible, have the hard drive power off after a period of no use and certain graphics chipsets, you can underclock, but I don't believe the Intel is capable of that. Turning things like wifi and bluetooth if you don't need them will help too.

All of this can be done in Windows, the reason I see better battery life in Linux is because the OS itself requires less resources, it writes to the hard drive less and it doesn't require the CPU to scale up as often during normal use.

If you have done all of the above, the best way to get better battery life, is to get a better battery. I believe the original battery is 2200mAh, this site lists a 4800mAh battery, I don't know how accurate that claim is though, I've never dealt with them.