The most common cause of this problem is the specific type of media you are using to create the Slayers Evox disc. Beleive it or not, every manufacturer and type of CD-R/CD-R/W has different levels of success being read by XBox drives and there are a number of them that simply will not work.
Make sure you've read the information
HERE in the tutorials section that pertains to creating backups and burning xISO images.
Also read the DVD/Backup forums and take a look at the running list there which details different types of media people have had success with. It's basically a community-input thread where people have posted their results with different media types - which should help you figure out if the CD-R/W discs you are using have any chance of working.
Also note that you cannot use CD-R media - it must be CD-R/W or DVD-R unless you have the Samsung drive. The BIOS doesn't determine which media labels can be read - this is controlled by the firmware which is programmed into the DVD drive. Therefore installing the M8 BIOS won't magically make the drive capable of reading CD-R discs.