Is it possible to control how often Windows Update checks for available updates? I would imagine a registry hack is necessary?
On Windows 7, you can use Local Group Policies to set Windows Update detection frequency.
Run this command:
Set the option that says
Note, nonetheless, that although detection can occur even hourly, installation will occur on a daily basis, minimum.
Indeed, you can set installations to be applied immediately, but this only happens to important updates that don't need a reboot (or to updates with a due date in the past, if you are using a WSUS server).
You can read this Microsoft KB article here: KB 326693, or simply run a task to do it whenever you want, with the command line option of:
Either way you do it, it is rather quick, easy and simple to setup.