In your case, if you're not getting a beep or anything after pushing the power button to start up, you'll need to start troubleshooting the internal parts of the computer. If you're not experienced with that sort of thing, then a reputable tech might be your best solution. If you want to give it a try, then I'd start with the power supply..Replace it, then move on to other parts such as the motherboard, etc..

Hope this helps.