|Look on the screen for the word "Setup". It should tell you which key to use (which takes you to BIOS). If you can get there, you don't need to change anything, but whether you can get there or not will help initial diagnosis.|
If it doesn't even get as far as BIOS or even attempting to load Windows then most likely it is a hardware fault.
Probably won't help but turn the computer off, remove the power plug (and battery too if it's a laptop). Hold the power off/on button in for 20 secs, then put the computer back to normal and try again. At least it is easy to try.
Otherwise there are a lot of possibilities, bad CPU heat-sink fixing, PSU, RAM and so forth. I would be inclined to try a Linux Live CD on it (which just runs from the CD and RAM). I use Puppy 4.3.1. for this. It will help narrow down what is wrong and eliminate Windows from the equation. It will not change anything in Windows when you boot without the disk.
Always pop back and let us know the outcome - thanks