how to update cocos2d version in a game

I've been using an older version of cocos2d for iPhone for an existing project -- never change a running system. Now I'd like to upgrade to a more recent version of cocos2d... I replaced all the cocos2d classes with old one; I get this error:

duplicate symbol _main in /Users/aqtoor1/Desktop/BlocksParty
[music] co/build/Debug-iphoneos/libcocos2d libraries.a
(main-D28BA02B69A7176A.o) and /Users/aqtoor1/Desktop/BlocksParty
[music] co/build/BlocksParty.build/Debug-iphoneos/BlocksParty.build/Objects-normal
/armv6/main.o

I replaced old cocos2d file for second with-in couple of days last time; I am getting some framework missing error now getting this one. I'm just stuck.开发者_如何学运维 :( Need help, I have to get this working to my boss, today. :(

I have done it by just replacing the cocos2d files - dragging them into the project. But before doing this make a copy of your project with the previous version (if still possible) That did it for me. As far as I know cocos2d is just a set of imported files anyway. The templates etc did not change, so there was no need to uninstall or reinstall anything.