Guardian: Greenpeace has accused three of the world’s biggest PC manufacturers of failing to live up to their promises to make more environmentally friendly computers. Hewlett-Packard, Dell and Lenovo have all been singled out in a report from the environmental campaign group, which claims they have failed to deliver new machines that do not depend so heavily on toxic chemicals. "HP, Lenovo and Dell had promised to eliminate vinyl plastic (PVC) and brominated flame retardants (BFRs) from …