The school's number or a classroom phone number if you have one. Make and model number usually on the front of the unit. Sometimes clones have no serial number or model number. We NEED the password for any and all security software installed. If you are not comfortable writing it on the repair order, put it in an envelope inside the box.
Most computer hardware has a one year warranty from the date of purchase.
If it's under warranty call before you send it in. In some cases a copy of the original invoice may be required for coverage. Be descriptive, use a separate sheet of paper if you like. Packing Guidelines Send only failing equipment. DO NOT send keyboards, mice, or power cords except in cases where they are specifically part of the problem or the device requires a special power transformer.