Disclosed are interconnectable personal computer architectures comprising secure, portable and persistent computing environments that provide secure computing sessions with persistence. The computing environments are implemented using a secure non-computing client device, such as a USB device, that interfaces with a host computer and, optionally, a trusted server. The secure non-computing client device is used to instantiate a secure BIOS and a secure cold or warm boot of the host computer, from the client device, in a host protected area of the host computer, or from the trusted server. The client device comprises a security device, such a trusted platform module, that encrypts and decrypts data transferred between the client apparatus and the host computer to provide a sealed computing environment on the host computer. The client device may implement keyboard logger attack prevention. The client device may also implement a high assurance guard to protect applications. The client device may also comprise security wrapper software that encapsulates malware processed by the host computer. Computing methods and software are also disclosed.