1. A method of checking an application program of a software platform in a Trusted Platform Module (TPM) to determine if the application program can be trusted by the software platform, comprising: virtualizing at least one physical platform control register (PCR) of said TPM for storage of a log of values representative of the state of the application program and its environment; providing a TPM interface that may identify a virtualized PCR by name; providing selective access to said identified virtualized PCR for storage of said log of values for said application program; and modifying or resetting said identified virtualized PCR to a value representative of a trusted state of said application program.