1stly we must verify evox working, do you see a purple EVOX sheild logo when you start xbox? If so modchip installed and working. If not verify contact and connection. Also if you used XControl to load the raw image, that you performed a X-Chip -> write changes ( This actually writes the chip with percentages shown )
2ndly we must look at media if #1 is working. Xbox DVD drives are very picky sometimes. It all comes down to compatibility with yoiur drive, if you think you have a Philips drive, easiest way to check is remove cover, a sticker on the DVD drive will indicate manufacturer. Now once comfirmed, you can do a search for drive manufacturer and media here on XS and see what media works with your setup. Now with drive compatibility coverred there is another issue......burnt image. Did you download an ISO or just straight files and you made a CD-RW out of it? If iso your image shoudl be good but if you had a directory, etc, you need to make a XISO format image to burn, there are many utilities available to do this. Do a search for XISO utility and you will get intructions on usage.
3rdly make sure you insert CD-RW facing proper direction with the label facing top of xbox, JUST JOKING!!!!!!