Actually both! The Practice Manager and TimeClock databases are driven by a Unix engine. The user interface is Windows based. The Unix engine is a secure, highly reliable, and extremely fast platform.The Windows interface is used throughout the world, but it does come with additional overhead.We strongly recommend that current versions of anti-virus and anti-spy ware be installed on all Windows workstations. The Practice Manager and TimeClock databases are included in our Virus Free Guarantee! (Q9041)