An "ASCIIZ" String means nothing more than an ASCII String terminated by a "zero". It works just like normal C strings or like the "PCHAR" type in Pascal.

The "MOV" instruction with control registers can be only executed at a privilege level 0 or it will cause an general protection error. If you are trying to execute it at Ring-0, it may still crash with invalid bit combinations in CR0.

But honestly I think you have no idea what you're doing and just found a few pieces of code which looked "cool" to you.