A Microsoft Virtual PC developer creates and manages virtual machines that simulate physical computers. This involves installing Microsoft Virtual PC software and configuring it to run multiple operating systems simultaneously. They build testing environments, simulate different scenarios, and troubleshoot virtual systems. They often work on migrating physical systems to a virtual environment, ensuring the compatibility and performance of applications across multiple platforms. They also ensure the security of the virtual systems, implement backups, and manage the performance of the virtual machines. Furthermore, they may train other team members on the use and management of these virtual environments.