Abstract: A method and a corresponding apparatus for metering usage of software products on a computer are proposed. The solution of the invention is based on the idea of associating each product with an installation signature (indicative of the installation of the product on the computer) and with a running signature (indicative of the running of the product on the computer). The products that are installed on the computer are asynchronously determined according to their installation signatures; in this way, any ambiguities (for example, caused by different versions and/or configurations of a product sharing the same executable modules) can be resolved in advance. Therefore, when at run-time the invocation of an executable module is detected it is possible to use only the running signatures to identify the corresponding product uniquely (without the need of additional information about the executable module, such as its size).