A spelldrive is a mystical computer book that can be used to cast spells. It uses "power points" to cast the spells, and each spell uses a different number of power points. The number of maximum power points a spelldrive can contain appears to be three. If there is a way to recharge the spelldrive, it is either unknown to Dib, or he lacks the capability to do so.
The user of a spelldrive does not need any specialized mystical knowledge to perform the spells, as the spelldrive does the casting itself.
When closed, the spelldrive resembles a thick hardcover book with strange symbols on the cover. However, when it is opened, a spelldrive can best be described as a type of laptop.
The number of spells that each spelldrive can hold is unknown. However, the one Dib uses to curse Gaz has at least five. Those five include Head Shrinking, Head Growing, Evil Eye, Berzerker, and Sense of the Shadow Hog. It is, however, implied by the showing of the clock while Dib browses, that the spelldrive contains many other spells, possibly thousands.