1. A method comprising: providing a first operating system configured to operate in a first computer system; providing first computer code configured to operate on top of said first operating system, said first operating system being configured to control physical input/output devices on the first computer system via first device drivers in the first computer code; providing a second operating system, different from the first operating system, configured to operate in a second computer system, said second operating system being configured to control physical input/output devices on the second computer system via second device drivers; providing an executable runtime component configured to take control of the physical input/output devices on the second computer system from the second operating system using the second device drivers that are normally controlled by the second operating system; modifying said first computer code by replacing the first device drivers in said first computer code with substituted device drivers, the substituted device drivers being configured to call said executable runtime component at runtime; executing said first operating system and said modified first computer code on top of said second operating system in said second computer system; and using said executable runtime component to bypass said second operating system and to take control of the physical input/output devices on the second computer system using the second device drivers that are normally controlled by the second operating system when said modified first computer code executes said substituted device drivers.