Which version of the E15 do you have? There are various models, and only a few have disk drives.
If there's no button, that's not a good sign. Are there any indicators (like DVD RW, CD etc) symbols where the drive should be? If not, you probably only have the bay for a drive, and there's not actually one installed.
Do a disk drive show up in "This PC" or in 'device manager'?