I recently encountered an issue where I hadn’t created an SSIS package in a while, and when I opened BIDS 2005 and said “Create New Project”, after naming the project and proceeding it barked at me, saying “Failed to save package file with error 0x080040155 ‘Interface not registered’. Turns out somehow my MSXML assembly files got unregistered. The way to fix this that worked for me, was to re-register msxml3.dll, msxml4.dll and msxml6.dll. Some said to just do 3 and 6, which would probably work, but it doesn’t hurt to register all three anyway. That did the trick!