Greenpeace USA said Tuesday that it painted a message on the roof of Hewlett-Packard Co.’s head office in Palo Alto and voice-mailed HP employees with messages from William Shatner protesting the use of toxic materials. The group claimed that its members had painted the words "Hazardous Materials" and Greenpeace on the roof using non-toxic childrens' fingerpaint. The message reportedly is spread over about 11,500 square feet. The Washington, D.C.-based group also said it had sent voice messages to HP employees from Shatner, who played Captain James T. Kirk in “Star Trek,” calling on the company to phase out toxic chemicals.