I have just had to buy 2 laptops at work.
I would reccomend looking at the HP 630, I paid under £300, for this you get:
Intel I3 processor 2.53 GHZ
2GB RAM
500GB hdd (I think)
Windows 7 Home edition
AMD chips are always cheaper than the equivlant Intel and IME/IMO better, hence you may be trying to figure out why there is a price difference between otherwise equally specced machines.
PLUS at the moment manufacturer are doing deals where you can trade your old laptop in for cash, T&C apply!
Alot of the problems are user error, i.e. using the laptop on the bed etc leading to overheating.
Martin