Most Windows programs use timing run off the PIT in the mobo chipset. This is normally set to the longest period it's capable of generating - 18.2 ints per second. I've seen several "speed enhancers" for DOS/Windows where all it does is increase the frequency of these timing interrupts - for example, raising it to 182 ints/sec. Since the game still believes ints are occuring at 18.2 ints/sec, it thinks ten times as much time is passing and runs its internal updating ten times as fast, making the game fly compared to normal.