Emulated read-write disk drive using a protected medium

Abstract

A read-write hard disk drive is emulated using a hard disk drive image file on a protected medium such as a CD-ROM, a written disk sector database, and file system filters. A file system filter intercepts file I/O requests from the operating system. Initial read requests are serviced from the hard disk drive image file. Write operations are directed to a database, such as in RAM. Subsequent read requests for previously written data are serviced from the database. Another file system filter monitors attempts to alter the file access attributes, and prevents pre-existing read-only files on the emulated drive from being written or deleted. The maximum size of the written disk sector database is the sum of sectors on the hard disk drive image file allocated to read-write files and free space. The emulated read-write hard disk drive allows for the execution of programs requiring a read-write native media.

Dependencies are inferred from the claim text.