which poly? NP and SP requires u to own a laptop, and
compulsory~ 
choose one dat best fits you and ur budget. For me, i got a not so
gd laptop coz i had my budget constraint (my gf always laughing at
my laptop for being a single core, hers is duo core and dat time
core 2 duo was not out yet) and now i am planning to change to core
2 duo

CPU or laptop? if u are going poly, i suggest u get a powerful
laptop. 3k for a laptop, u can get very good ones.
for the time being, i dun recommend u to change to vista, if u
going poly, nvr ever consider vista, the software dat poly might
wan u to install for ur course might not be vista compatible, so
dun take the risk. win XP service pack 3 is going to be out, so
from this, i think dat XP will still be arnd for quite
sometime.