Pc wont boot

Have you recently experienced a power surge or had an electrical (thunder) storm in your area? Potentially your motherboard and/or processor could be toast since the fan running and CD Rom drive opening will continue to function because they receive power separately from the motherboard via the power supply. If you have access to a different compatible processor, you could try to install it in the motherboard to rule out a motherboard failure, otherwise you're looking for a new motherboard.

Make sure the monitor video and power cables are properly plugged in. If you have more than one video adapter in your computer, try plugging the video cable in the other one. Try another video monitor just to confirm that your monitor is not defective, or test your monitor on another computer.

If those steps don't reveal the problem, your computer probably has an internal problem with one or more of these components:

-Power supply module
-Video adapter
-Motherboard
-Processor.

This will require testing by an experienced computer technician to determine what's going on.