|You do NOT need any drives connected in order to POST. So, the drive controllers are not the reason your not seeing anything. |
My guess is that you may have disturbed something. Have you tried to start up while observing inside the case? When doing this is there any indication the computer is attempting to start?
Try clearing the CMOS by using the jumper on the motherboard or by removing the coin battery for 20 seconds. Be sure to unplug the computer or if your power supply has an On/Off switch use it to cut power. Don't forget to restore to the jumper to the run position.
When you restart the computer you must immediately enter the BIOS (setup) screens and reset the date, time, boot order, etc.
When you went back to the integrated graphics did you connect to the same port on the motherboard?