Solved: Add a second SSD drive - HP Support Community - 6859134
HP PRODESK 400 G3 SFF i5-6500 3.20GHZ 8GB 256GB SSD UHD630 W10P GRADE B | eBay
Amazon.com: HP ProDesk 400 G3 Small Form Factor, Intel Core Quad i5 6500 up to 3.6 GHz, 16GB DDR4, 512GB SSD, WiFi, BT 4.0, DVDRW, VGA, DP, Windows 10 Pro 64-Multi-Language Support
HP ProDesk 400 G3 SFF – Specs and upgrade options
HP Prodesk 400 g3 Unboxing RAM upgrade DDR4 and upgrade to windows 7 to 10. Prodesk 400 g3 i5 SSD - YouTube
HP ProDesk 400 G3 SFF Core i5 3.2 GHz - SSD 512 GB RAM 8GB | Back Market