computer dead

[#1]

Sometimes when I try to switch on my computer nothing happens ,the switch has no power ,no fans ,no lights nothing ,as if there is no mains power;the leads are o.k as I have changed it with the monitor one, and back again ,both work the monitor, then something happens and it is all O.K, I am reluctant to switch it off once going. Obviously it is a power problem ,but it will run all day and night O.K. Can anyone tell me whats wrong as I think this may be something simple Thanks  E
AMD Athlon 1.40
512 MB  Ram    Windows XP  Prof

[#2]

Please don't take this the wrong way but judging by your post I would assume that you don't have too much knowledge of the internals of a computer. If this is the case I would suggest asking a more knowledgeable friend to have a look at it or pay a local company to check it out.
However a few thoughts if you would like to investigate further.
It could  is a duff power supply.
Can you borrow another one and test
It could also be the motherboard or the connections to it
However it would be worth doing a few diagnostics first. Do you know which motherboard you have and is there a manual with it.
What we should be looking for is diagnostic lights on the motherboard and whether they light up when the computer fails to start.

[#3]

Or it could be a faulty on switch
John

[#4]

At the expense of being too simplistic. Do check your main power lead is fully pushed home in it's socket, it's quite possible to have it; not quite in fully and making intermittent contact, which can have you spending hours stripping down and discarding lumps of expensive goodies, when the answer was ridiculously simple...I know it's happened to me, we've got a cat that likes to get behind under my desk and push it's way into a corner, loosening up the cables and connectors to my PC (those that don't have a secure lock of course) it's warm in there I guess!!

[#5]

Well thanks for the ideas , I dont think it is the lead ,but may be just behind it  maybe the fan dosn,t start or the switch is faulty. I know little of the inside( I was a radio mech 1954 National service so ohms law is about my limit) and I have "two big boys"in the business,who usualy see to that sort of thing for me, one built the computer.it is one of his cast offs They both live far away. I may have a look inside later but meanwhile am advised to leave it on until help arives later in the week or next . Will let you know what happens Thanks  E

[#6]

Check the switch it has to simply connect to wires for a second and release. often it sticks on and this kills the power its not like the good old switch that was of and on.
Is there a light inside the case on the motherboard when its on? a lot have it and its normally on even when the power is off(but plugged in). if you can see the light it 89% likely its not the power supply

[#7]

I'm a firm believer in Occam's razor.  The simplest solution is often the best, and should at least be discounted before moving on to something more complex.
John

[#8]

Strictly Occam's razor says that the solution with the fewest assumptions (not necessarily the simplest) is probably the best

[#9]

Fair point

[#10]

It looks to me that help is on the way eventually and therefore if the problem is less than 240volt...leave well alone until that help arrives.

[#11]

@stathe
I had something like this a long time ago, which I don't remember getting to the bottom of.
Removing the power lead or switching off at the plug socket for 5 or ten seconds allowed the PC to boot normally.
Hope this helps.

[#12]

Some time ago now , but senior son advocated a new power supply and then decided also another hard disc , I always spend more than intended with him at the helm all is well but I have an anoying problem(This was there before the repairs)  as the computer freezes some times or always, if left on for a long time, I wonder if I should have bought a new computer.I have searched this on google and there seem to be fixes for this that you have to pay for ,reg fix etc ,are they any good or could somebody point me to free ones  Thanks  E

[#13]

Re  Computer freeze                                                Thank You Am unable to download Windows Defender as it says my copy is not valid I have done the Virus check and  C Cleaner to no avail I am not sure how to do the rest . The power is now fine  Regards  E