you have set up your box in a way that the Live CD nuked it. You need to reboot with the bootdisk, and delete xboxdash.xbe. Then put your original reatil dash back on, and name it xboxdash.xbe. Then put your evox dash on, and name it evoxdash.xbe. Then turn off the box. With the chip enabled, evoxdash.xbe will boot, and with it disabled, xboxdash.xbe will boot. If you have more questions, there are many topics on this. Check the newbie and Live forums with the search button.
To lock the drive, you need a program called Config Magic FINAL. This will allow you to lock it, but don't mess around with any of the other functions, because if you press the wrong buttons, your could rape your xbox completly. Drive locking is necessary for using the original dash on bootup, and for going on live. There are many tutorials on this, but not all of them say to use Config Magic FINAL, this is your best bet, because it is easiest to use and allows you to recover your drive your xbox dies for some reason. If you have any more questions, send me a PM and I'll help.