A computer enclosure includes a chassis and a cover. The chassis has a first hole, and the cover has a second hole which is substantially coaxial with the first hole. A securing means engages in the first and second holes for mounting the cover on the chassis. A shield is fixed on one of the chassis and the cover. The shield defines a through hole communicating an outer side of the shield with the securing means and a receiving hole intersecting the through hole. A rotating block is rotatably positioned in the receiving hole between the through hole and the securing means. The rotating block includes a blocking portion configured to block the through hole. The rotating block defines an access hole in the blocking portion. The access hole is configured to communicate the through hole with the securing means by rotating the block to align the access hole with the securing means.