The dc7800 desktop computer from HP provides several key energy efficiency and environmental advantages: 1) It has an 80%+ efficient power supply, low power processors and chipsets, and HP BIOS settings to reduce energy usage. 2) It meets various global environmental standards and certifications and is designed to be easily recycled with recycled materials. 3) HP offers services like take back and recycling programs to ensure safe disposal and reduce environmental impact over the product's lifecycle.