The two power buttons do carry out the same function of powering up your system but in various ways. The first button to the right-hand side is the regular power button for starting your system normally (either Windows or other operating system). The second one to the left-hand side is called the 'QuickStart' button. It is used to power up the system into the ASUS 'Expressgate' which is meant for Linux operating systems. If you aren't having a Linux OS like Ubuntu or Mint in your computer this button would be of no great use to you.
There are two major causes of such problem and they are: 1) Your RAM(Random Access Memory) might have gone bad. In that case replacing it with working one is necessary. 2) The GPU chip might have malfunctioned and that would require a tech specialty to fix. Either reflowing it or replacing it. If the chip is not found it is time to get a new motherboard. For the issue with your DVD, it is possibly the optic lens is failing and that means you would have to replace it or get another DVD writer.
I am only going to speculate on this issue because it doesn't really look like the fans are the culprit here. My suggestion is to check for any blocker, broken piece or materials that are interfering with them.
There are many things which can cause a system to overheat. The major ones are as follow for a Windows operating system: 1) When the cooling fan has accumulated debris or the vents are blocked. 2) The heat sink is faulty thereby losing the ability to dissipate heat properly from the processor. 3) Thermal compound on the processor has completely dried up and can no longer carry out its function. 4) Running high specifications-consuming applications on a low system hardware. 5) Some malicious software using up the memory and more part of the system storage can be a culprit. To find solution to your system you would have to tell us more about the conditions of the system. Does the system whiz heavily at some point in time? What application do you usually run that makes the temperature to go up? What is your system configuration? At this point in time you can try to prevent the vents from anything that can block them. Place your system on a flat table or desk when using it. Listen for changes to the noise of...