XDA forum member NetRipper has written a neat application that gives you the power to not only control the CPU speed of your HTC HD2, but also to overclock to some degree.
LeoCpuSpeed reads the CPU speed of your device every half second, and can stress the CPU to show 998MHz when it is at 768Mhz. The app gives you control of the speed by use of a slider or pressing 768/998 presets, as well as the option to set speed at boot, and of course overclocking.
Currently, overclocking only works on AC power. When running on battery power, LeoCpuSpeed will apply the overclock but will this will be undone by the OS within 500ms.
For more information on LeoCpuSpeed and to download, visit the application thread.___________________