To me it sounds as if your mobo took a dump on you, have you got a old one to see if the rest of the equipment works with the new one?
I have to agree with Chris, the mobo sounds fried. You can take your CPU and find another p4 system thats compatible to check that but it could be an awe full lot of trouble. When you say case fan do you mean the CPU fan or an air intake fan? What I am getting at is, is that fan plugged into the mobo or directly into the powersupply?
Sounds like the mb is the culprit. I know this has nothing to do with your pc not booting up, but did you set that new optical drive as master. You mention that b4 when u tried to install both drives one didn't work. Maybe 'cus you didn't set one for master and other slave.
Anyway, mb is probably lost.
Good luck
If the case fan sputtered when plugged into both PSU's either the fan is going bad or the PSU isn't being supplied with enough power. Check the dip switch on the back to make sure it set to the correct voltage for your location and try an outlet in a different part of the house, i.e. one on a different circuit.