Notes about the XIB file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The XIB file type is primarily associated with 'Interface Builder' by Apple Inc.. File contains "flattened" archival UI object(s) streamed to disk. Content loaded early in program execution. XIB files are a statically stored representation of the set of interface objects used by the application and their relationships. Similar to NIB (NeXT Interface Builder) files so XIB probably means Mac OS X Interface Builder.