Virtual DOS machine
NTVDM cannot run DOS games on computers of today. Emulation is only provided for simple peripherals. For example, sound in NTVDM can be limited. Windows NT only updates the screen a few times per second when DOS programs write on it, and they can't emulate high-resolution graphics options. As software runs at the speed of the CPU, all timing loops stop too early. This either makes games run too fast, or causes the software to not see some emulated hardware peripherals, because it can not wait that long for an answer.