I'm not sure exactly what the issue is from your description but can I suggest trying these steps.

unplug the vga/DVI cable from the monitor and check for the monitor's self test feature which means it goes from standby to on- make sure your not overlooking a monitor issue here.

Look out for the bios reset on the motherboard that should resolve any CMOS corruption issues- one of the symptoms could be a slow system fan. -http://support.gateway.com/s/MOTHERB...94Rmvr24.shtml

finally- check the keyboard lights(you know- caps lock, scroll lock - num lock) make sure they toggle on and off -these can indicate that your system is processing fine and it might just be a video issue.

let me know how you get on.