laptops take 4200 or 5400 rpm drives traditionally. 7200 rpm drives for laptops are at a premium, but any SATA 2.5" drive will do, just pick the size or price your willing to pay. all SATA300 is backwards compatible with 150.
If the google'd specs of that laptop are in fact stock including vista disable drive indexing, and clean up the software before changing it up.
I'll have to do the drive indexing thing, but I always cleanup the bloatware that comes on company built systems like that. I'm also going to add a couple gigs of ram to her system because the 1GB stock isn't cutting it at all.