If i cant use key to deactivate my anti theft system what else can i do to get car st
 

I have a 96 nissian maxima i only have half of my key in ignition and i have the other half and it starts car , but my anti theft system has been triggered and my car want start . I cant use key to put in my car door which is how i have gotten it off in the past. Please any help would be greatly appreciated

Talk to a local locksmith. They can (at least some can) put some kind of tool in a good working lock and it "reads" the key pattern so the locksmith can cut you a new key or two.