Old projects are not running in new iPhone SDK 4.0

I have a UICatlog project downloaded from apple development library. It was running fine w开发者_JS百科ith 3.0 Base SDK, but when I upgrade xCode SDK Version 3.2.3. I am getting an error:

error: There is no SDK with the name or path 'iphoneos3.0'

What do I do?

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Change the Base SDK setting in the Project Info to iPhone Device 4.0.

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Check that you aren't changing the Base SDK for the project and not the current target. The current target base SDK setting will override the project settings. Also, if you wan't to support older platform versions, make sure you set Deployment target appropriately.