Desktop with windows 7-OS not starting

hiii all,

For last few day my desktop (lennovo -K210) not starting soon after,the cpu start button is pressed,The fans just running again and again for few mins(almost 15-20 mins) after few mins the cpu(Fans) stops running...and all the lights goes off...then if the cpu-start button is pressed the computer starts....the most amazing thing is at the start-up no error shows up.....it starts normally..

And the one main event i noticed is this happen only when the computer is started after long time(8-10 hrs) of shut down...,once i got same problem as i said above and after few mins it started...just to check the problem i shutdown the computer and started again...it started at the first press of cpu "start"no delay on 2nd start-up.

I tried the following,but no use at all:

1.restored the system configuration by start-up utility
2.reset system cmos through jumper
3.changed new motherboard battery

Help would be highly appreciated,thank you

Need help with this problem...

Hiii,no reply so far...i need to confirm wheather... I naratted the problem correctly or..nobody had experienced this problem so far...plz some one reply

=======================bump=======================

You need to post your message and wait, someone will be along.

Bumping is not appreciated and might just delay a reply.

Have you done startup repair? Can you boot into safe mode with networking? Turn on-Press F8 repeatedly, and select it.

hii, startup repair couldn't find any error...and "safe mode with networking" is booting without any error....reinstall the os is the only way to fix this problem.i guess.....

Have you tried a Restore Point?

Try unplugging the HD to see if it starts correctly every time. THis can be caused by bad code in the boot sector. What's required in that case is to back up your files, wipe the HD with Diskpart Clean Command to run Clean Reinstall - Factory OEM Windows 7

If not then you have a hardware problem most likely in your Power button assembly or Power Supply. To test each you can bypass the switch by crossing the leads, or trying another PSU. Psu calculator - Windows 7 Forums