Got Backup? You can delete them, but if disaster occurs, you'll lose any info that's not been committed to the database, AND any info that's been committed, but not backed up yet. If you do nightly FULL backups, and up to the minute restores are not important to you, turn on Circular Logging. This will make exchange overwrite every 5th log file so they won't consume more than 30MB or so total disk space.