According to my database of knowledge there is no Free Antivirus for Nokia 6600 Device! U can try out McAfee Antivirus, Norton-Symantec Antivirus!
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You can't get apps without a regerstartion but i found that zedge is good short regersration. (www.zedge.net) the games are good though, i got cooking mama from it, its good quality as well :-D.