It says unregistered sim card

Check this site:
http://www.ehow.com/how_7196572_activate-unregistered-sim-card.html

How to Activate an Unregistered SIM Card eHow

The cell tower might be down !!

Suggest remove the battery and then the sim card then reinstall the sim card and the battery and power up.

Your sim may have been inactive for a long period of time. Sim's don't need to be registered. try a new sim and if it still say "unregistered sim", contact your phone's service provider. good luck!

remove sim the reinsert. turn phone on again

unregistered sim usually means the sim no longer works.. i.e its disconnected by your service provider..

hello,for the activation of your sim card,all you need to do is just to contact your service provider and it is going to be activated.
pleasse kindly rate the solution if it's helpful,

take care.

Invalid SIM and Unregistered SIM are two different problems. Invalid SIM means the phone is locked to a certain company and you are trying to use a SIM card for another company. Unregistered SIM means the SIM card you are using is not active and you need to contact your service provider to get it activated. In order to unlock the phone so you can use anyone's SIM, you must contact the provider that the phone is locked to.

you seem card does not seem to be active that is the only way you will get that prompt of unregistered sim.

So contact your mobile provider and query your card