After installing some programs on a new hard disk I shut the computer down. On the next boot, the keyboard and mouse were disabled, this was from the very moment Windows 7 started.
It sounds like the software you installed has conflicted with or caused problems with your hardware drivers. I would recommend you boot into Safe Mode, which starts Windows with a minimal set of Services and Drivers.
To Boot into Safe Mode start your computer and keep pressing F7 before windows starts to load. You will then be presented with a menu, select safe mode.
If your keyboard and mouse now work, try uninstalling the program and seeing if you can boot up normally again.
It may also be worth removing any other USB devices and trying a different keyboard and mouse (one may be faulty) and trying to boot again.