I don't think you can if you haven't already enabled USB debugging to unlock the bootloader. Best you could do is try flashing stock firmware to try and repair it. I assume you have tried factory reset in recovery?
Also, if it doesn't appear in ADB when you type "fastboot devices" (I don't even know if that is still the command lol), then ADB probably isn't set up correctly. Unless I'm remembering wrong and you need USB debugging for the device to show at all. It's been a while.
Oh yeah, go to the XDA forums.