My Computer won't work - it is dead?

[#1]

My PC was working this morning, tried to switch it on again a few days later, but it is dead.
Is this a power supply problem - it's showing an output between a couple of wires of 0.15V
I don't want to replace the PSU if it's a motherboard problem.
Please help!!!!

[#2]

Quote from: A

My PC was working this morning, tried to switch it on again a few days later, but it is dead.

I don't understand this sentence.
When you switch it on are there any lights or LED signals on the motherboard

[#3]

Disconnect everything from your PSU except for one single fan that should be connected directly to one of the Molex connectors. Then, get a small piece of wire, paper clip, or suitable object and short the green pin and a black pin on the 24-pin connector on the power supply. Your PSUs fan should spin along with the fan you have connected to it. If this is the case, your PSU may not be receiving the power on signal from your motherboard and you should consider other causes of the problem you’re having.

[#4]

Which end of the spade are you holding? 
Although you probably don't have one to hand, I recommend something similar to these which has found it's way into my toolkit
Allows you to test a completely disconnected PSU for recommended voltages and clamping times.
B.

[#5]

Thanks Strat,
I tried shorting the green & black (without disconnecting anything though), but nothing happened.
However, no fans etc spun - still dead.
Are we looking at a motherboard failure?
BTW Barry I don't want to spend £25 for diagnose something that I've never seen happen before.

[#6]

You checked the mains fuse? These have been know to blow occasionally.
Failing that, as Strat said disconnect EVERYTHING from the psu and then test with one fan by shorting that link. It maybe some thing is pulling the psu down. IF it powers the fan, try the mb without any drives then work up as it powers if no power with just fan then probably the psu, got a spare?

[#7]

At the end of the day a new PSU is relatively cheap, certainly compared to diagnostic kit, motherboards and processors.
AND it's the commonest thing to fail.
So, I'd just buy a new one and try it.
Simples.  
PS:

Quote from: A

My PC was working this morning, tried to switch it on again a few days later, but it is dead.

Time travel? 

[#8]

Simples?
Mains input is O.K. - (it has a little neon indicator)
I'll try disconnecting all the peripherals and then buy a new PSU - expect that's £40+ groan...

[#9]

£40? Depends on rating and whether you're prepared to take a risk on eBay........
I always aim for something a step up from the one that failed, but still tend to buy cheap. 

[#10]

Ebuyer psu's aren't bad depends on the power you need the 500/550W ones for about £20 were good value last time I bought one (a few years ago though)

[#11]

Thanks - I'll try Ebuyer then
My PSU iss a 650W Atrix 500T - if that is meaningful.
I'm sure 550W is O.K.

[#12]

is this one any good ?
http://www.novatech.co.uk/novatech/prods/components/powersupplies/novatech/nov-psu650.html

[#13]

I notice that the fan is at the top - my present PSU has a fan on the same side as the mains plug (and another fan where the wiring spaghetti comes out).
Does this sort  of thing matter?

[#14]

That fan will almost certainly be on the bottom when installed in a standard case.  
But check your mounting screws and orientation to be sure.

[#15]

You really want a fan facing the mb and one out the back
So that air is sucked out of the pc.