After you find the Varia Suit, Adam tells you to go to the Data Room in Sector 5 (ARC) to get Ice Missiles.
Find the Security Room
Use the Navigation Room, then go to the right, through the Save and Recharge Rooms. In the next room, climb down the ladder, then jump onto to the ladder on the left side. There is a Zeela on the wall on the right. Kill that Zeela, then climb to the top of this ladder and shoot at the right wall to open a hole. Shoot a missile into that hole to open a tunnel. Roll through it and go through the door at the end.
Be careful of the Chute Leeches that are hiding on the floor in this room. They are hard to see if you are moving quickly. When you approach a Chute Leech, it will jump upward then float slowly down, dropping a harmful blob as it floats.
Go to the bottom of this area, then go to the right and follow the path through the room to reach the lower right door. Go through.
The fast-moving enemies in here are called Wavers. Shoot them quickly to kill them before they can hit you. Go to the right and you will see a red hatch. Ignore it and go downard, and ignore the grey hatch below. Go to the left from the grey hatch and your path will be blocked. Shoot the floor where it touches another section of floor on the right. This will open a hole. Go to the left from there and go through the door.
Kill the Zeela in this room, then go to the far left, then start running to the right, shooting as you go to make sure you go through the door. You will Speed Boost through the floor. Make your way downward, then go toward the bottom right of the room. Bomb the small block that is in the way, then go to the right and go through the door there.
Bomb the wall, then avoid letting the Wavers hit you. Go through the door on the right.
In this room, go down below, but don't go through the door htere. Instead, bomb the floor and fall down below. Go through the door on the left, then in the Save Room, go through the door on the left. Keep going to the left until you reach the Security Room. Connect to the console to unlock yellow hatches. Then go through the door on the left.
Go up this tall room, killing Zeela as you go. The X from the Zeela will respawn into new Zeela if you don't collect them. At the top of the ladder, shoot the blocks above you to get rid of them. You can shoot diagonally by pressing the left shoulder button. After shooting the blocks, get on the ledge to the left and go to the left side. Shoot the ceiling to break a hole, then go through and go to the right. Go through the door there.
After you go through the save room, open the gate and go through the door on the right. Keep going to the right until you reach the large room that you were in earlier. Go to the right and jump up through the hole in the ceiling, then go to the right and go through the door there. Shoot open the gate in this room and go through the door on the right. Use the machine in the Data Room to get Ice Missiles. Now your missiles will freeze things.
Go through the door on the right and shoot a hole in the floor. Fall down the hole, but beware of Rippers as you fall. Keep going downward, and when you see a ladder on the right, grab onto it and climb to the top. When the Ripper at the top is centered, shoot it with an Ice Missile, then jump on it and go through the door on the left.
Slowly approach the Energy Tank, because it's another enemy in disguise. Shoot it with a Missile when it floats up. Then bomb the left wall to reveal the real Energy Tank. Exit this room, then go to the bottom of the tall room. Roll into a ball and enter the small space on the right, then jump up and go to the right to enter a hidden passage. Go to the right side of this room and shoot the ceiling and jump up. Kill the Zeela but don't absorb the X. It will turn into a Chute Leech. Approach the Chute Leech to make it float up, then freeze it with an Ice Missile and use it to reach the ledge above. There is a Zeela on the ceiling, so kill it but don't absorb the X. It will turn into a Ripper. When the Ripper is under the left side of the notch in the ceiling, freeze it and jump onto it, and shoot the middle of the notch in the ceiling to get a Missile Tank.
Go to the bottom of this area and roll back through the tunnel to return to the previous room. Go through the door on the left. After the Kago becomes taller, freeze it, stand on it, and shoot the ceiling. Jump up through the hole, then go through the door.
Go to the left side of this room and kill the Zeela, but don't absorb the X. After it turns into another Zeela, kill it and don't absorb the X. It will make the Kago become taller. Go to the right side of the upper area and freeze the Kago with a missile, then run to the left while shooting your beam to open the door and make a running start into the next room. You will Speed Boost through a wall in the next room. From there, go up to the upper left area of this room and go through the door on the right.
From the door, go up, then go to the right. You will reach a dead end with a narrow floor above you. Shoot the wall to the right to break it open. Go to the right, then jump up onto the ledge on the right, and shoot the wall to the left to open a hole. Roll through the tunnel and you will fall through a Pit Block at the end. Go to the upper left door of this area, and go through.
Go upward from the door, and at the top, go to the left and fall to the bottom of the area. Go to the left, then go up. To go any farther up, you need to freeze the Chute Leech at the peak of its jump, so do that. You will find another Chute Leech here. Freeze it at the peak of its jump, then jump onto it and go through the upper left door of this area. Take the missile tank from this room, then go back to the previous room.
Go down to the lower left corner of this room. Go through the yellow door and shoot the Geruta with two Missiles, then drop a bomb in the top right corner of the room to reveal a Missile Tank. Take it, then go through the door on the left.
The computer will announce an emergency. Don't panic. Go to the top of the tall room and go through the door. Be aware that after you use the Navigation Room, a countdown timer will start. Go through the Save and Recharge Rooms, and use the Navigation Room. Adam will tell you to quickly go to Sector 3 (PYR) and shut off the Main Boiler. You have 6 minutes.
Go to the left, up the elevator, and go to the Sector 3 elevator and go down.