This is really cool... except that it won't work as described! Or at least, it sure as hell will not work very well.
A Cadmium-Sulfide photocell only changes resistance, it does not generate voltage. This might work, kind of, with a microphone input for a PC, but most mics these days generate a signal, they don't just change resistance.
To make a better version of this, you would want to use something that creates a voltage, not just resistance. Like a solar cell. Find one that works with the frequency of light you are using.
By the way: this short video also glosses over the very big problem of alignment, if you are using a laser. They have to be in pretty exact alignment, and at exactly 90 degrees to the window, to work at all.
