Once you have removed the tray screws, be careful lifting the tray out -- the hard disk cable runs under the tray to the header on the mainboard, and is VERY SHORT. And the header is VERY FRAGILE.

So just lift the tray up enough that you can reasonably grab onto the disk cable connector underneath, and gently unplug it from the mainboard header.

Most empeg troubles are due to fatigue on that header, so due care is needed here to avoid adding new failures to the already dead machine!

Cheers