Abstract: Applications running in an API-proxy-based emulator are prevented from infecting a PC's hard disk when executing file I/O commands. Such commands are redirected to an I/O redirection engine instead of going directly to the PC's normal operating system where it can potentially harm files in on the hard disk. The redirection engine executes the file I/O command using a private storage area in the hard disk that is not accessible by the PC's normal operating system. If a file that is the subject of a file I/O command from an emulated application is not in the private storage area, a copy is made from the original that is presumed to exist in the public storage area. This copy is then acted on by the command and is stored in the private storage area, which can be described as a controlled, quarantined storage space on the hard disk. In this manner the PC's (or any computing device's) hard disk is defended from potential malware that may originate from applications running in emulated environments.