This is going to be a bit long -- but very detailed, so please read itcarefully. There are several reasons that an xbox 360 system will haveproblem reading discs. The error messages also vary from unreadabledisk, no message at all but the game skips, "please insert disc in a360 console" to "open tray." There are a few reasons this may happen:
1.Bad disc. Check the back of your disc for scratches. If it looks good(or plays fine in another console), then the disc is probably fine.Also-- try more than 1 game to be sure.
2. Bad laser. The XBox360 has a DVD drive very similar to a PC's DVD drive inside. The drivecontains a bunch of parts including a few motors and gears and a laser.The laser is the part that actually reads the disc. The reality is...with all the hours and hours of gameplay, lasers do eventually wearout. The laser isn't very easy to replace, but it is replaceable. Youcan find any and all XBox 360 lasers at the following website:http://store.richspsxparts.com/xb360ac.html
3.Bad DVD Drive. Sometimes other components inside of the DVD drive canbecome bad such as the motor that spins the disk, the motors that openthe tray, etc, etc. You can get a new DVD drive to just replaceeverything, including the laser, in one shot but there is a catch. TheXBOX 360's DVD drive is tied to the motherboard using a software lock.The easiest way to overcome this lock is to buy the exact samemanufacture DVD drive that is in your system now, remove the circuitboard from the old DVD drive (which contains the software key) andtransfer the circuit board into the new DVD drive that you purchase. Ifyou do this simple procedure, there is no flashing involved. Thefollowing website carries DVD drives and also provides instructions onswapping the circuit board from the old drive into the new one.
XBox 360 parts: http://store.richspsxparts.com/xb360ac.html
DVD Drive Swap Info: http://store.richspsxparts.com/imnooninxb36.html