My Sony Vaio desktop won't turn on

I have a Sony Vaio Desktop that I bought from 2003 that worked superbly all the way until two nights ago, when I could not turn it on. I checked all of the plugs and extensions and they working just fine. The computer runs on Windows XP and the model number is PCV-2234. The Sony website doesn't even have this model listed. I am not computer savvy at all, especially when it comes to its inner technological workings. I'm scared to open up my desktop in case I mess something up. Can someone give me step-by-step instructions on how to fix this problem? The computer was honestly working fine so I'm so confused what could cause it to suddenly stop working.

Any help is much appreciated! Thank you.
 
There are many things that could have gone wrong.

First, can you tell me what happens when you push the power button, nothing at all or is there any sound from inside the box like fans running?

If it is completely dead your power supply has probably failed and you would need to get inside the box to replace it. Borrowing a power supply would be best just incase it is something else. It could be something simple like the power switch or something severe like the motherboard.
 
Back