Could be a PSU or MB problem. Any strange sounds from the case or lack of sound?
Try some easy things first:
All cables (monitor especially) plugged in and secure?
Do the IDEs work in another computer?
Re-examine your code and look for any errors that might have had some negative effect.
Can you boot via Safe Mode?
Do you have a rescue disk?
Try booting via USB and open source software.
Then check the PSU, the fans, all internal connections and work though it all.
Need to methodically work through the possibilities to see what, if anything, can be discovered.