pc boots sometimes sometimes no

[shawn123]

hello geeks,
i own a pc with gigabyte k8m800m mobo,sempron 2600 processor 512 mb ddr400 ram,2 nics,award modular biosv 6,windowsxpsp2

the problem is that when i press power button it doesnt start at times....no post,no bios loading etc....
even adsl router doesnt show lan connection..lights..the usb mouse has the power light on though little slimmer than when computer boots .no hard disk drive lights or cdrom leds glow this time..

some other times it loads after a interval of 1 or 2 minutes after i press power button more than once usually and waiting for2 -3 minutes.....

there are times when a power failure occurs and i usually quit...but generally through the shut down button.

mobo onboard lan is dysfunctional after a lightning and i have added 2 nics ...one of which maynot be working i have not checked this..

any ideas?thanks in advance

[DIY Guy]

It sounds like a power problem. You also mentioned lightening so anything could be fried inside the machine.

the most basic place to start is with the power supply. It may be dead and requires replacement. However, even after replacement, you may find that the motherboard or other components are fried.