Let me add a bit to this thread ....
Dummy files are added to the discs so the important data is closer to the edge of the disc. The PS2 is capable of readign discs on 2 modes:
CAV - Constant Angular Velocity
In this mode the speed of the disc is fixed and the DVD drive CPU has to poll the disc data varying with the width of the track. Since the laser runs a smaller distance per revolution on the inner tracks the data rate is smaller close to the beggining of the disc. Pushing the data to outside DOES a HUGE diference as you get aproximately 12x at the inner ring of the disc. what you get at the outside ring is 24x data rate. That at the drive's maximum speed for CD.
CLV - Constant Linear Velocity
In this mode the laser is running the disc at the same speed regardless where it is at the disc. This read mode is used only at 1x and 2x (Reading audio CDs and PS1 discs) Since the data rate is aways the same, there is no reason for a PS1 disc to have dummy files.
The scratching noise (sounds like a "shhhhhh" noise) is caused by the tracking and focusing of the lens on the disc. Since it's a recorded media and you probably burnt it on a very high speed it's signal is weak and the drive is having trouble to focus it. So since it's difficult to read, the drive microcontroller raised the gain control for the focus, sending more energy to the focusing coils, causing the noise to be audible. It's done automatically and there's nothing you can do about it besides changing the media brand and/or writting it at slower speeds. The same way the PS2 can control the focus/tracking gain automatically it can also control the laser gain automatically so reading CDRWs and badly burned CDR discs are lethal for your laser. A good burn really sounds like a silver when it's running.
Another weird/wrong thing that people say is that DVD rips break/burns the laser. What break/burns the laser is the boot method (at the time we were using DVD rips we were mostly doing swaps for boot).
If you use a swap method, the PS2 will auto adjust to the disc it read 1st (Swap magic, Game shark, Action Replay, etc etc) and you will force the laser to run at a lower gain than it would with a CDR/DVDR, making it harder to read. To solve this people "tweak" the laser pots. That solves the problem but as drawback the laser lasts half of the time it was supposed to last.
SCPH-10000_GH-001 SCPH-15000_GH-003 SCPH-18000_GH-008 SCPH-30001_GH-005 SCPH-30000_GH-016(V4) SCPH-30001_GH-010(V4)
2xSCPH-10190, 2xSCPH-10350, 2xSCPH-10280
"**** j0 hackers!"
-Sjeep (As seen on TOXIC OS ELF...)