Strange Behavoir of my PC

Morning Geeks!

Please can someone help diagnose my problem.

A few months ago I bought this 2nd PC from a friend, but since the 1st day I have been having an issue starting the PC. Sometimes the screen does not get the msg to turn on. Now, I turned it of properly everytime, but the next time I go to turn it on the screen stays off. Theonly way to gget it working is to turn off the mains power to screen and PC, and then turn it all on again, hey presto the screen gets the msg. I did start putting the PC into sleep, rather than off, and this worked for a while, I could turn my PC on my pressing the keyboard, but now this is failing and I have to againg turn it off at the mains.

Another problem that might be related is that sometimes my PC turns itself on, usually in the middle of the night, very bizzar.

Can anyone help?:confused

 

If the monitor is not getting power, and the PC is not getting power, then the problem is likely in the power strip or surge protector. But if the monitor does have power (inidicated by an orange light when it's powered on but not rec'g the video signal) then problem is likely with the PC. The first thing I'd do is unplug the power cord from the PC and open the case. Faulty capacitors commonly cause this type of problem. Pictured below are faulty and healthy capacitors. Carefully search the motherboard and look at all the capacitors and compare them to the pics below. Just one popped/failing capacitor spells the end of the motherboard and can possibly damage other components from the hard drive to the CPU and/or video card. Also, a failing power supply can cause these problems. If you have access to a known good power supply. Hook it up and give it a go and see what happens. If you don't have 2nd PSU, you can get a used one at a local PC shop (use it for diagnostic purposes only) for only $10-$15. The last thing it could be is a sketchy power switch on the case, but this is fairly rare, but I've seen it happen fairly often in certain HP computers where there's a big cheap plastic 'spring' that fails preventing the big cheap plastic button from making contact with the actual switch. As to the PC turning itself on, I have only seen this behavior in certain Dell towers that have an "auto-on" feature in the BIOS, but there may be other PCs out there with an auto-on feature; make sure it's disabled. If the feature is disabled (or not even in the BIOS) then again the problem is likely one of the above problems: bad motherboard, bad power supply, bad power switch. Here's the capacitor pictures:

Normal healthy capacitors look like this:
http://tbn3.google.com/images?q=tbn:l-O3uyAZWlRbFM:http://www.hardware-one.com/reviews/msi6309/images/capacitor.jpg http://www.fotosearch.com/bthumb/GLW/GLW137/gwc118050.jpg

Failing/leaking/popped capacitors look like this:

http://tbn2.google.com/images?q=tbn:Y5WuxQTQI_nreM:http://www.op911.net/photos/story/capacitor.jpg http://tbn3.google.com/images?q=tbn:n6qnVlzrMn1XaM:http://i.ehow.com/images/GlobalPhoto/Articles/2162895/BadCapacitor01-main_Full.jpg

Sometimes bad capacitors won't actually have the crud leaking out the top as in the pics above, but if the top of the capacitor is not PERFECTLY flat, then it is failing. Even a very, very slight 'popped' top is bad news.