Hello again friends and thanks for looking my problem. I have just built a new Pentium4/3.0/ECS,FX648 mobo. Anyway after the initial build and test the machine was left for a week before being powered up again. Then i got a CPU has been changed message which i associated with a low CMOS battery. I press any button to continue but the machine fails to boot(just blank black screen). Once i changed the CMOS battery then the machine seems to boot OK. But although it looks like my problem is solved i just did not think a dead CMOS battery would stop a machine from booting(especially with me pressing the any button to continue once i got the CPU changed message). Any comments???????