Obsolescence is the state of being which occurs when an object, service or practice is no longer wanted even though it may still be in good working order. It refers to something that is already disused, discarded or antiquated. For instance, the architecture of hardware may change because machines are replaced, which means that some types of software will no longer be available, supported or maintained. In this respect, digital signature, a fundamental aspect of digital evidence in eDocument may be a problem. The digital signature software may still be available but the digital signature might have been applied using a version of the software compatible with Windows 98 but not the current Windows XP, Vista, etc. The signature software tool may have been overtaken by a new version rendering the others obsolete. Where the digital signature is not migrated to a newer version, its integrity becomes questionable.