Antivirus software blocks malware; malware disables antivirus software. Cookie blockers delete cookies; websites reinstall them. Applications install new system components; operating system updates delete them. In numerous cases, one program deliberately interferes with another. These program-vs-program cases challenge the legal system to find a coherent way of distinguishing dangerous programs that harm users and make computers unusable from the valuable programs users rely on to keep them safe from the dangerous ones. Any such distinction, however, must rest on an underlying theory of user autonomy. Looking closely at program-vs-program conflicts can help us understand where current legal theories of what users want go wrong.