Final answer:
DDR and DDR4 are the two memory types installed using DIMM slots, representing different generations of RAM technology.
Step-by-step explanation:
The two memory types that are installed using DIMM slots are DDR (Double Data Rate) and DDR4. DIMM (Dual Inline Memory Module) is a series of RAM (Random Access Memory), and DDR and DDR4 refer to different generations of this memory technology. SSD (Solid State Drive) and Flash memory are not installed into DIMM slots; SSDs are typically connected via SATA or NVMe interfaces, and Flash memory is often used in USB drives or memory cards.