car won't start, door locks , windows won't work, brand new battery

With the information you've given, unfortunately, it'd be hard to pinpoint a specific component causing the issue. Newer cars use complex computers/modules that can and will disable functions if certain signals are missing or parameters aren't met. The first thing that pops into my head is the "immobilizer system". Often times after a battery is replaced, the security system will disable the vehicle until the system is reset. Otherwise, the problem could be one of many different things. Sometimes an expensive diagnostic machine/scanner will be the only way to verify some of these issues. Could you elaborate on what happened when the vehicle died to begin with that prompted the battery replacement?