I'm thinking of getting a new computer, and selling my old one. How do you know what to sell it for?

I have an IBM pentium III, 1133MHz, 261,000KB ram, windows 2000, 26 gig HD..it's a laptop. I think I got it in 02-03..any idea what i could get for it...

Also, whats a good brand of computer to buy? (I want a laptop)

/edit
Oh yeah, I duno about the stats for it..I looked under something on the comp to see...