A computer enclosure includes a chassis with a supporter attached therein and a drive bracket assembly with a sliding member formed thereon. The supporter has an arced surface. A plurality of parallel ridges are protruded from the arced surface and arranged along the arced surface. The drive bracket assembly is mounted on the chassis, and configured to rotate on the chassis between a securing position where the drive bracket assembly is horizontally located on the supporter and different inclined positions where a corresponding ridge of the plurality of ridges blocks the sliding member to prevent the sliding member sliding freely by gravity.