Just tried my new Asus HD 7870 Direct CU II on my PC, and have a corruption problem when start Windows 8. I see a bright neon green display with horizontal streaking everywhere, tinged with purple/pink colour. My PC build is as follows:
ASROCK B75 Pro 3 Motherboard
8GB DDR3 Dual Channel RAM
128GB Crucial SSD
650W Artec Green PSU
Internal Graphics Card works fine (Intel HD 4000) and have had no problems with other external cards. I also notice that when booting to the BIOS, the display is enlarged, and overlaps the screen by 50%
I would talk to ASUS about this. It sounds like the card may be DOA (dead on arrival). The only thing that would possibly cause this is bad configuration in clock settings or lack of power, but as it is new and you have a 650W power supply, I would suspect the card is bad.