Your computer must have:
64MB of RAM (128MB recommended)
800MB of hard disk space free
CD writer, tape streamer, NFS share or some way to backup the backups :)
It is recommended that your computer have very good airflow. The backup with Mondo Rescue and Mindi Linux will utilize your CPU, CD drive and fixed disk(s) like very few other applications. With a few hours of system backup activity, computers without sufficient airflow may show symptoms such as not burning full CD discs. The solution is a $20 or less additional fan at your local electronics discount store.