My machine never starts in one go. you have to unplug the power cord from the power supply or sometimes switch off the main power. I do this 2-3 times then my machine starts and remain on until I wish. I've changed the power supply, but it doesn't seems to be the problem...please advise...thanks

When the machine doesn't start, how far into the boot process does it go? If you changed the power supply, then the mother board is next. Check for loose connections such as a loose printer cable. Better yet, disconnect everything including the CDROM. Of course, don't disconnect the HD.

Wierd!? Stuck or sticking front panel power button?? Try removing the 2 leads of the front power button from the mobo, and and simulate a bootup by just briefly shorting the 2 pins together with a metal object (ie: screwdriver)... carful not to touch any other pins though. If she boots right away then the button is faulty... if not.... then I'm stumped!

thanks for all replies...The machine doesn't start at all...only the processor heat sink fan moves a little bit and then stops...the computer only starts when the post light blinks on the keyboard when you switch on the power, if there is no light then it will not start..is it some kind of earth problem with the power supply / motherboard?

If this is an ATX mboard where both the power and reset switches connect to the mboard, both those switches in an ATX case are the same type (momentary), and in that case blackbill may be on the right track - try switching the connectors for the reset and power switches and using the reset switch to power up. If that doesn't help, your computer must be plugged into a grounded (earthed) AC power source via a grounded cord - if it isn't fix that.

"I've changed the power supply, but it doesn't seems to be the problem..." Your system is far from being power hungry, a 250W-300W PSU should be fine, but it has to be a good one. You didn't say what you bought, but if it's a generic cheapie, it *may* be the problem. Here's a decent 250W unit for about $26: http://www.newegg.com/Product/Produ...