I would recommend to get lenovo. Dell is not too bad, my first laptop was Dell Inspiron.I have a HP dv2000 series with 12 Cell battery, 2.2Ghz Core Duo, 2GB RAM, 64MB Nvidia card, with Vista Premium, the performance is quite good. I heard HP is offering laptops with slots for 4GB of RAM. For vista I would recommend to have a 256MB Nvidia card instead of the Intel Graphics card.
Vista is slow. I see that internet explorer crashes more often. Firefox works fine in Vista. But even with 2Gb of RAM it is very slow. So I would recommend XP. When you buy a laptop with windows vista, right click on My Computer -> properties -> check for the windows user experience. Anything with overall rating 4.5 and above should be a good buy.