In a virtual computing machine, a system and method that dynamically patches the interrupt mechanism (in interrupt vector space) of a host computing architecture with guest mode software. Significant increases in performance are achieved without depending on the host code. A patching mechanism evaluates the operating system version, processor, and code to be patched. If patchable, low-level interfaces are created dynamically; a dispatcher is written into an unused location in vector space, and instructions copied from each interrupt vector to be patched to a guest interrupt vector. For an interrupt, the new, patched instructions branch to the dispatcher, which then branches to the appropriate patched interrupt guest code. If the processor is operating as a virtual machine, the guest interrupt code handles the interrupt, otherwise the original copied instructions are replayed, followed by execution at the original host instruction in vector space that exists after the copied and patched instructions.