Associated .I01 software

Windows
I01 file extension
DVD Shrink Temporary File
The .IO1 file format is used by DVD Shrink during a full-backup to the .ISO format.
During the backup, the software created a series of temporary files, the first being .I01, followed by .I02, .IO3 etc. It seems that DVD Shrink is more likely to do this if the drive you are backing up uses the FAT32 file system.
To mount the resulting image, you'll need to use a tool such as Daemon Tools Lite.