I01 file extension

It's an ISO mds disk image split with DVD Decrypter (to avoid problems with some file systems with large file sizes). You must use the mds file to burn/mount the image or convert it to an iso.

Use sfv file to check integrity of the files to burn (mds file + i00 file (i01 file, i02 file, i03 file, i0[number] etc).

Here are some programs to use mds files with differents O.S. (It's possible do it in different ways)

Windows: DVD Decrypter or imgburn, Alcohol 120% etc.
Linux user's: use mdf2iso
Mac users:
Rename the files with extension i00 to i0x as follows:
- filename.i00 => filename.iso.001
...
- filename.i05 => filename.iso.006
Then use the program Split and Concat to join the files and make an ISO.

If you don't know how to burn the files. Use each program's help guide.

This i01 file type entry was marked as obsolete and no longer supported file format.

This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.