Hi Raistmer,
CodeXL 1.1 allows you to install on Windows Vista. It is not included in the system requirements as Vista is not a formally supported platform. This means we have not vetted CodeXL functionality on Windows Vista as we do for the formally supported platforms.
Bottom line - you can install CodeXL 1.1 on Vista, but functionality on this platform is not guaranteed and we do not plan to fix any Vista-specific issues that may arise.