1. Hint stated "Brad sought for help from his friend Allan Latham, and he received a software for it in Jan 1999"

Allan Latham developed a program Jphswin back in 1999.

2. Downloaded Jphswin and loaded the given jpeg (HIDDEN_INSIDE_3) and seeked the file without using any passphrase.

3. Outputted the file as 'Hidden_File'

4. Opened the file with Notepad++ and obtained the flag: yea_I_loVE_TENNis_matCHEs

Original writeup (https://github.com/RandomPost/CTF-Writeups/blob/main/Hidden%20Inside%203.txt).