Help with choice of version, and dual booting. Newbie here

[ReubenBartolo]

Hi.
I have an Acer 5920G with 4Gb RAM and 250Gb Hard disk space.

On it I have Windows XP installed, which I need to use, so I cannot remove it. It is partitioned in two, one for OS and application installs ( 60Gb) and the rest for data.

About me: On my home PC I have Ubuntu installed, which I am a bit confident with. It is good for my needs.

The issue is that sometimes I simply want to browse, or watch movies on my laptop, while travelling. So I would need a nice and simple OS that would boost my battery life. That is why I am looking at Linux.

So I have two questions.

1) Can you please tell me, or point me in the direction of, some data to make an informed decision about which Linux I should go for, to boost my battery life.
How much do I want it to last? The more the better. 5 hours is better than 4. While 6 is better than 5. Obviously this should not come at a cost of functionality. I need an internet connection, web browser, something to watch movies, etc. =) (In case of a tie, I would always prefer Ubuntu, given my previous experience with it. Also, I have tried Live CD, and it works. )

2) Can you please tell me, or point me in the direction of, some information as to help me in setting up safely my laptop as to dual boot. I have found a lot of websites( I have done my homework)

I just want to know what you people think is the best procedure to follow, even if it is simply a link.

Thanks in advance =)