The Dell Precision M6600 Mobile Workstation Supports up to 3 Drives. (One 2.5" Solid State Drive or Hard Drive in the Removable Drive Bay and/or One 2.5" Solid State Drive or Hard Drive in the Internal Drive Bay and/or One mSATA Solid State Drive) Note: If installing a 2.5" Drive in the removable drive bay, you will need the 2.5" Drive (HDD1) removable drive bay caddy p/n PCPR1 for installation. If installing the secondary 2.5" Drive in the internal drive bay, you will need the 2.5" Drive (HDD2) secondary internal drive caddy p/n 07N5J for installation.