METHOD OF REPLACING THE IDENTITY OF A FILE WITH ANOTHER AS PART OF A FILE OPEN REQUEST IN A COMPUTER SYSTEM

In an improved method for accessing files in a computer system, file open requests are intercepted at the level of the operating system. The identity of the file to be opened is extracted from the request and a determination is made as to whether the identity of the requested file should be replaced with the identity of a substitute file to be opened instead of the requested file. If it is determined that the identity should be so replaced, the file open request is amended by substituting the identity of the substitute file for the identity of the requested file, and the request is passed on to its original destination for execution. This technique can be used to cause execution of a substitute program without the knowledge of the user. As an example, software metering can be implemented in a network system by substituting a different program from that requested when the number of copies of the requested program in use on the network has reached the maximum licensed number, so as to provide a user-friendly rejection of the program execution request.