Disclaimer notwithstanding, with Pesach approaching, it's time I talked about it. I owe at least that to the increasing number of visitors who come here searching for "chametz". So here I bring you some Pesach cleaning guidelines for the office. (For previous Pesach-related posts, see here and here.)
I don't know why I haven't seen this issue addressed elsewhere. As always, I am not a rabbi. Don't rely on me for halachic advice; always make sure to ask your own rabbi if you have practical questions. And remember to take appropriate safety precautions in working with hazardous materials such as cleaning products.
Office Pesach cleaning guidelines
If you never eat at the computer, no Pesach cleaning is necessary.
If you sometimes eat chametz while working at the computer, the keyboard must be thoroughly cleaned of crumbs. There are two main approaches among the halachic authorities. The lenient position deems it sufficient to turn the keyboard upside-down and shake it vigorously until no more crumbs fall out. A minority of posekim, however, require the keycaps to be removed (this can usually be accomplished easily with a bit of leverage from a screwdriver) and the interior of the keyboard to be vacuumed clean of crumbs. Please consult your rabbi for advice.
Either way, if you plan to use the computer over Chol Hamoed, the keyboard should be covered. Some computer shops and kosher supermarkets will carry clear plastic keyboard covers which suit this purpose. Look for those marked Kosher for Passover.
If you consume hot liquid chametz at the computer, such as instant noodles or some types of coffee and hot chocolate, the keyboard must be kashered using hag'ala. Plunge the keyboard in a large pot of boiling hot water for approximately 15 seconds, or until sparks fly. The entire keyboard must be kashered, including the cable. We take no responsibility for the continued functioning of the keyboard after this procedure. If this is not possible, buy a new keyboard for Pesach.
Though it is smaller and less complex than the keyboard, the mouse is more problematic to clean for Pesach, as the mouse has a tendency to "drag-and-drop" chametz from place to place. Either buy a new mouse for Pesach, or learn the keyboard shortcuts.
A flat-screen monitor (LCD display) does not get hot and thus need not be kashered for Pesach. It is sufficient to clean it with a moist cloth.
A conventional CRT display, however, can get quite hot. If you use your monitor to heat up chametz, you must kasher it using libun gamur. Generally, this means heating it up until the surface glows. This can be done by applying a blowtorch for several seconds to each area of the surface. Make sure to unplug the monitor before trying this.
It is recommended to test the procedure on a small, concealed part of the monitor before applying it. If your monitor does not hold up well to a blowtorch, consider buying a new monitor for Pesach. (You owe it to yourself, anyway.) If this is not an option, you can cover the monitor with shelf paper or aluminum foil. Otherwise, avoid placing food directly on the uncovered monitor during Pesach.
If your hard drive has chametz in it, you have problems that Pesach cleaning cannot solve. It couldn't hurt to defragment, though.