System Boot Problem

[Nuguy]

Just finished putting together a new pc. All components individually are ok. The problem is that when powered on the system does not boot up. Monitor says "Signal Not Connected".Checked everything I can think of. I have tried two different graphic cards but still did not boot. The m.b. is an Asus PT4, cpu is P4@1.9 these are new components I am in question of perhaps. Any help would be appreciated.