MGS2 (still have it) is definitly an iso. Pretty sure all our games here are either iso or img with the occasional cd based PS2 game being a bin. Virtual drive should work and also if it's burned correctly but simply running it through PCSXs file system is probably the best way to go.
The reason I asked for a screenshot is to see if he "unpacked" the iso itself - only other thing I can think of (again lol) is that maybe his PCSX2 settings are wonky - from another game perhaps and a reset to default settings or a reinstall of PCSX2 may work.
Also to cover all bases I want to make sure that he has the BIOS file for the PS2 and that it's in the correct folder.
Edit: the game themselves work (although I only tested mgs2) it's just something very simple somewhere that we're overlooking. Hell I used winrar to extractand it worked fine.
