Std debugging is to pull parts until the PC posts. When it posts it will beep. Then put parts back in 1 at a time until you isolate the failed part.
start with pulling all external wires including keyboard, mouse, network, video, etc. POST? no - pull all PCI cards. PSOT? no-pull all memory. Etc.
this ref may help http://www.tomshardware.com/forum/261145-31-perform-steps-posting-post-boot-video-problems