If Xenia says "Cannot find valid title," your ROM is either corrupt or encrypted. Many public archives provide already-decrypted ISOs. If you have a raw ISO, you need to run it through Xbox_Backup_Creator to extract the $SystemUpdate folder.
Xenia stores save data in your local Documents\xenia\content folder. If you are moving between different versions of the emulator or different PCs, this is the folder you must back up to keep your progress. Advanced Archiving: Extraction & Tools xenia roms archive
. While providing XBLA titles in various formats, these sources are often unreliable, and the Xenia team advises dumping personal game discs . Explore the Internet Archive collection to see available XBLA titles. XBOX_360_XBLA directory listing - Internet Archive If Xenia says "Cannot find valid title," your