Hardships of upgrading

Question

I recently upgraded to Snow Leopard, the new XCode, and the new IPhone SDK (3.?).

Now when I load some old IPhone projects downloaded in association with a text book, they won't compile because the compiler is looking for iphoneos2.0.

Where in the information associated with a project is the iphone OS version identified, and can it be changed?

Thanks in advance for any help.

John Doner