computer starts to boot when switched on at the mains mrroutethen switches off before boot complete, fan stops, flashing led stops flashing and remains on,no signal displayed on monitor .

computor is set to remain switched on at all times. started to switch off after approx 1 hr then decreased in time until now it will no longer boot any advice pse

mrroute, November 2012

Fans stopping, especialy if it include the power supply fan, mean that the power supply disjoncted, usualy from overheating.
It looks like there is a problem with your power supply. Initialy, it was probably only overheating due to dust buildup, but, over time, that heat seems to have caused some other damage.

If that's the case, you need to replace the power supply. Chose one with approximatively the same power rating as the original one.

You may also have dust buildup on the CPU heat sink, or it's fan no longer work.
Open the case. Using a can of compressed air, blow away any dust in the CPU heat sink. Power up for a few seconds to see if the fan do work. If it don't work, replace the fan.

Electro, November 2012