I used to use an Inspiron 8500 (512MB RAM; GeForce 4200 Go 64MB RAM; Pentium 4 2.4GHz). It is semi-playable in raids with the settings at default, at 1680x1050.
I would crank down video settings to minimum and set it at a very low resolution- you might at least be playable with that, although it definitely won't look very pretty.
You should definitely look at getting something more powerful, though, if you really want to play games with a laptop. Dell sells laptops that run WoW decently (although not at max settings) for around $1000 or so.. the really high end ones can do WoW with everything maxed out, although they are much pricier.