How can i do a hard reset on coolpix l27 ?

SD cards have a slide switch along one edge. The position farthest from the metal contacts locks the card, protecting it from writes. The position nearest the contacts unlocks the card.

Have you tried going to computer, browse files copy and paste. Then tried updating firmware on camera?

I assume you meant to download pictures from your L27 to your computer.

The best way to download pictures from your camera to your computer involves removing the memory card from the camera and plugging it into a card reader (either built-in to the computer or connected via USB). This is likely to be faster than connecting the camera to the computer, and won't run down your camera's batteries.
Once the card is plugged in, it will appear to your computer as a removable drive. You can use the operating system's drag&drop facility to copy pictures from the card to the computer's hard drive, the same way you copy any other files. Or you can use any photo management program such as Picasa ( http://picasa.google.com ).

Are you sure the battery is still ok? As soon as de capacity of a battery is not enough the camera's tend to shut down. PLease also check if the contacts of the battery and from the camera in the battery compartment are clean and shining.

Remove the battery for 15 mins. Replace the battery and go to the menu settings and set the date and time.

Check if the pictures on downloading to the PC had errrors if so the camera needs attention as there is possible failure in the CCD /imager of the camera.
You can remove off battery and replace after few hours for a hard reset, if this wont help get in touch with Nikon service support
www.support.nikonusa.com/app/answers/detail/a_id/16357/~/???product-information---coolpix-s230
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Try a camera reset. Go into the menu and scroll to "reset"...follow the on-screen instructions.

Remove memory card from the camera, connect it to computer using cable, copy pictures.

Look for a reset function in camera manual If no manual download one - if nada, then contact Nikon customer service for inside assistance with dilemma. Due to high cost of camera repairs you just might have to go shopping.

Try the menus, if they work, possible that the ccd is bad.
Here is a link to the Nikon Advisory.
http://www.nikonusa.com/email_images/nikonusa/service_advisory/coolpix.html