Original spec for this laptop is 2hrs 35min battery life when new.
HP Pavilion dv6000 review - CNET You may get better with a new higher capacity battery. The downside is going to be XP and the hard drive. This laptop is roughly 8 years old and most hard drives start to get flakey at that time or before with moderate use. I would get a nice 32gig thumb drive to back up any files of value just a precaution.
I have found good batteries on both Amazon and Ebay for my ibooks. Just look at either the buyer comments (Amazon) or the seller ratings (Ebay.)