My phones battery is going dead every 8 hours

dead batteries possibly

First try charging the device for at least 8 hours. If the issue continues the device or battery may be faulty and need replaced / repaired.

Try this:
Many post suggest using "advanced task killer" but none of them really gave the perfect settings for it, well i finally found them out myself

The settings i use : Auto Kill Level ==> Aggressive
Auto kill Frequency => When screen off
Security Level ==> Low

Additional tweaks are: 2G only
disabling WIFI and Bluethooth
disable GPS and positioning

source:
http://forum.xda-developers.com/showthread.php?t=707573

How long have you had the device?

Over time the battery will deteriorate and lose capacity, some companies batteries are known to be worse than others.

If you've had the phone for more than 8 months I recommend you purchase a new battery, if you've had it less however I would get the phone checked for any faults.

www.gsm.com

Thanks for writing Fixya. I am Marion and let me help you with this.
Please be reminded that brand new phones or newly purchased phones should be charged around 8 straight hours because the battery is definitely drained.
I would highly suggest you to charge the battery for 8 straight hours and try to open your phone if it work.
Now, if you still encounter the same issue. It would be best if you bring the [hone to the nearest service center since it is still covered with warranty.
Hope this was helpful. If you have any queries, please feel free to contact us back.

It could be some application, that is draining the batt. Do a hard reset and see if any better.

Purchasing a new phone is easy and everyone is always in a hurry to use new phone but never go through the manual properly. You did the same you didn't put the battery on charge for 24 hours. Now to check your phone take another charged battery for nokia put it inside your phone and start it. It will deffinetly work. In order to revive your dead battery keep your battery on charge while the phone is switched off for minimum 24 hours. If it gets revived its ok or else purchase a new one.

DO YOU HAPPEN TO KNOW THE CODE TO UNLOCK THE PHONE WE HAVE?I WOULD APPRICIATE IT GREATLY IF U COULD HELP ME OUT....THANK U VERY MUCH.

is it shutting off because the battery is dead or is it just random?