i have a d3415 one day i tried to power up the computer and the monitor would not kick in come to find out the cd drive won't open and hard drive wont either so i replaced the power supply still does the same thing i'm thinking mother board could use some advice about this.

Try replacing the memory stick or if there is more than one take one out, swap them around and see if that fixes the problem.

Is the bios battery flat?
it's about 3/4 inch across, take it out and test it, it should be about 3v. You'll have to reset the clock on the computer if you get it going again.

Is there any lights on or any activity at all?

Have you checked to see if the power button is working ok and is connected to the motherboard?

All the fans or just the one in the power supply? If the power supply is starting up check you have a 12v and 5v supply on one of the spare power leads, check for voltage between the black and red wire and then the black and yellow wires.

Sounds like the motherboard is powering up but not posting. I would try disconnecting the cd/ dvd drives, floppy drive and harddrive and see if it's still not posting. If it does, switch off, connect one drive at a time and check again. If it doesn't I would say you have a motherboard fault because you,ve already tried the bios battery and memory.

nope did nothing

replaced it with a new battery does same thing

just the blue power button

when i press the power button the fans kick on
all the fans come on

unhooked both drives just powered fans hooked drives back up one at a time still only powers fans

Either motherboard or processor faulty most likely then. Have you got another processor to try?

All these single line posts have been covered in general here:
Tutorial: No POST (Power On Self Test)

Edit:

Thread cleaned up considerably