Important questions need asking:
Will they be buying the extended warranty?
Will they pay the extra £20 to have Linux pre-installed, or will it run Vista Premium Ultimate Supercomputer Edition Pro X?
When it dies in 6 months, will they have to pay the shipping costs to have it returned for a 2 week repair?
When it comes back, will it have been reformatted with Vista, regardless of its previous configuration?
Will it come back at all, or will Dell lose it somewhere along the line and have to supply a new one?