International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Upgrading or replacing production systems is always a very resource-consuming task, in particular if the systems being replaced are quite specialized, such as those serving any Flight Test Ground Station. In the recent past a large number of Ground Station systems were based in Digital’s VAX/VMS architecture. The computer industry then expanded very fast and by 1990 realtime PCM data processing systems totally dependent on hardware and software designed for IBM-PC compatible micro-computers were becoming available. A complete system replacement in a typical Ground Station can take from one to several years to become a reality. It depends on how complex the original system is, how complex the resulting system needs to be, how much resources are available to support the operation, how soon the organization needs it, etc. This paper intends to review the main concerns encountered during the replacement of a typical VAX/VMS-based by an Intel-Windows NT-based Ground Station. It covers the transition from original requirements to totally new requirements, from mini-computers to micro-computers, from DMA to high-speed LAN data transfers, while conserving some key architectural features. This 8-month development effort will expand EMBRAER’s capability in acquiring, processing and archiving PCM data in the next few years at a lower cost, while preserving compatibility with old legacy flight test data.