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The newbb 2.0 is an official Module so the Tables sure will change, but only to add more fields create new tables which are needed delete not needed Tables, thats all.
The newbb 2.0 is a Module and use nearly only Core Functions, but didn´t change any off them, this should be obvious for any Module, makes your live with updates easier and you are more protect, because update to 2.0.7.3 is a security update to gives you protections.
So back to your questions, this is nonsence what you have heared. Not core files will be touch, changed, delete or what else. Updating after installing the newbb 2.0 to XOOPS 2.0.7.3 or to further Versions is no problem.
Greetz Predator
