The .daa file extension (Direct Access Archives) is the format created by PowerISO much similar to large ISO files. It is commonly used because it compresses original data, can be password-protected and is able to be split into smaller parts. The .daa files are most commonly used online to distribute large files on the internet through P2P downloads or through the bittorrent network. Even though PowerISO is free to use as trial, it has limits regarding how big file size you can open with it. » Read more: Extract and Open .daa Files without using PowerISO