If you would like to clean the Front Case, simply take a damp cloth and wipe it down. Make sure it fully dries before reassembly otherwise you risk water damage to the PC.

If cleaning the Optical and HDD Drive be very careful not to drop or slam the HDD as you will damage your DATA and OS. Meaning when you reassemble the PC, you will not have an Operating System to come back to. Also be careful not to spray to close to parts as condensed air has high moisture content at close range.