A heat dissipating device includes an object, a housing having a chamber for receiving a driving device which includes a spindle extended out of the housing, a fan device is attached to the spindle of the driving device, for being rotated and driven by the driving device. A cap includes a locking device for locking the cap to the housing, to attach and to secure the housing to the object. The cap includes one or more catches engageable into lock notches of the housing, for securing the housing to the object with the catch. A guide arm may be attached to the housing for receiving one or more electrical cables.