Metal Gear Solid 1 "Please Insert Disc 1" Issue

Okay, so I own a copy of the game for PC. I decided to install it, doesn't work, so I searched it up installing the fixed version, installed it to the same directory where I installed the one on CD. When I tried starting it up, everything seemed to work fine until starting up a new game, which keeps telling me to "Please Insert Disc 1", which confuses me, since I own the game legit with the CDs, using Disc 1. I tried doing other options like using Compatibility Mode, starting it up as Administrator, and switching it to 640 x 480, disabling full screen optimizations, nothing.

Not sure what I'm doing wrong and wanting to see what I can do with the CD that I own for it.