Here are the Simple few steps showing how to fix Different Sim Detected (emergency screen).

Step 1: Download iFunBox from http://www.pars-gsm.com/Downloads/ifunbox_en.zip
Step 2: Run iFunBox and Sync it with your iPhone
Step 3: Go to /private/var/root/Library/ and delete the original lockdown folder then put this Lockdown Folder from download RapidShare: 1-CLICK Web hosting - Easy Filehosting
Step 4: Reboot your iPhone!Download

Use at your own risk.

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