I have quite a lot

Question

I have quite a lot of experience building PCs. Have just installed Asus P5E3 MoBo Core2 Duo E8400 CPU 2MB OCZ DDR3-1333 memory. It will not power up properly. All fans spin up briefly and HDD LCD flashes once, then it goes down again. This then repeats every 5 seconds ad-infinitum. Same symptoms in a different case/power supply/HDDs/graphics card, even with memory removed. Cannot even get into BIOS. Any ideas - MoBo, CPU?Pete how