Q: Can I unlock FFXI's achievements if I completed their requirements while playing on the PC or Playstation 2?
A: Yes you can. The only carveat is the "Gold Ballistar" achievement: You can still do it with this, but the achievement has to be unlocked within a week of earning it (have to speak to the title changer NPC with the key item in your key item list) or you will have to do it again. Other than that, it doesn't matter what platform you use while playing. You only have to be on the xbox to get the achievements added to your gamertag.