Most laptops are at least dual core these days so that helps. However be careful because some of budget dual core intel CPUs are quite slow and not worth it, even if they look like a bargain.

If it will be running Vista also make sure it has plenty of ram. 2GB as a minimum, and 3GB if possible. laptop ram is very cheap these days (£24 for a 2GB SODIMM) so it shouldn't be a problem. And also to get Vista running smoothly a reasonable graphics card is needed. Nothing fancy if you are not intending to run the latest DX10 games, but avoid the integrated Intel graphics cards as they are very crap. Make sure it is an ATI or nVidia card.

For value for money I always like Acer laptops. Their build quality is quite good, but not quite at the same level as HP/Compaq or IBM. If you really want a robust laptop, especially if you intend to take it places, then one from those two companies is recommended. Although you will be paying more for the name.

Dell laptops are also quite good. But you are tied into buying their own parts for any upgrades so do get ripped off.