Here is what i found on abits website
8.3. Guru check ATX power supply ready signal Power on -> Stop at 8.3. 12V 4 pin plug disconnected or power supply damage Check 4 pin power plug or replace power supply
what it is saying is check your 4 pin is it disconnected or you might have a dieing power supply. Can you boot in to windows is this a error on the screen? beep codes? http://www.abit.com.tw/faq/code.html here is the link to the info