My computer wont start up straight away, when holding down the start button it revvs like an engine and after 3 minutes if I am lucky it will turn on.
The computer is an emachines about 2 years old and this has intermittantly happened over the las t6 months now it just wont start.
I have checked all the usual things such as power supply loose wires cleaned out the cooling fans but it hasn't helped.
I dont know if this has anything to do with the problem but the system used to hang for a while before loading windows, again loads of memory & minimal start up programmes yet it still hangs.

Open your pc case. I think the whirring sound comes from the rotating fans (processor fan, power supply fan, video card fan, and the case fan). Observe their rotational speed.

I have an interesting problem like this...I'm not sure how to repair it yet, but I have found a temporary solution: Unplug the small, 4-wire connector that comes from the Power Supply from the logic board. Turn on the machine and let it run for 15 secs or so. Now, you HAVE to unplug the AC cord from the Power Supply...pressing the button seems to have no effect, no matter HOW long I hold it. I reconnect the wire and VOILA! the thing boots like there's no problem. There is no BIOS update available (as of 2008-Jun) and the only card in the machine is the modem that it came with, so I'm gonna replace the CHEAP 120w PS with a beefy one and see if it's the PS.