twilight

I need a laptop for school. I have a very limited budget and I am having a really hard time finding what I want for the price. I only have 500-800 to spend. And I really don't know much about computers. Where's a good place to buy, I've been looking around online and I just can't seem to find what I want,

But I kind of have an idea of what I want....
long battery life
hopefully home vista but I read that it runs really slow on only 512MB and I cant find a good 1GB for my price
CD/DVD Burner w/ RW and Dual layer
light weight
doesn't have to be super fast but I don't want a slow comp
not to concerned about the brand, I don't know which ones are better

Those are the main things I'm looking for, so if anyone could help me that would be awesome.
I also have another question, I need microsoft office but its so freaking expensive, and I found Open Office on Ebay for bout $5. I don't know anything about that though. Would it work okay?