Monitor won't turn on :(

If, as you say, you have tested the monitor on a working PC and have tested the old PC with a working monitor, the answer is clear. There is a problem with the old PC, not with the monitor. If you see absolutely nothing on the screen at all when you switch the PC on, then it is NOT even doing its initial boot (which is contained in ROM on the motherboard). The first thing I would do, then, would be to change the small backup battery (a flat cell somewhere on the motherboard) which is what keeps the BIOS settings in memory when the PC is switched off. If this doesn't work, then it's something more serious. Replacing the CPU is unlikely to solve the problem and, in any case, is expensive. It is probably better to let that PC find its way to the Recycling Centre!

What do you mean it doesn't "turn on at all?" * Do you see anything when the machine starts up? * Can you boot a DOS diskette and get video? * Can you boot in the Safe Mode and get video? * When you remove the video cable do you get a message on the screen of the monitor saying that there's no video signal? * Does the AC of the monitor turn on. In otherwords, is the monitor really on - getting AC? * Does the video work with another monitor? Take your machine to a friend's and try his/her monitor. * What video parameters have you set? Maybe you're exceeding the limitations of the monitor. I was responsible for college computer labs and classrooms. A favorite trick of the students was to change the settings to have a screen resolution that was beyond the capabilities of the monitor. When that is done you would seem to have no video and just a blank screen when you boot up. The answer, obviously, was to boot using the Safe Mode and change the resolution back to something within the capabilities of the monitor.

I think you may have a need to remove your Bios and replace it with a New One , try to clean your RAM slots

well, my friend faced a similar problem, but it was defect on his mother board, but that may not be the situation in your case. Is the cpu of your old pc really getting on?? IS the lights on the keyboard blinking while on ON the cpu?? Can you hear the beep sound, that normally sounds when you switch cpu ON?? And is the small LED lights on CPU blinking while you switch it on??