Hi ValorHeart,
Optiplex 380 has three variants: Mini-Tower, Desktop, Small Desktop. Mini-tower has two (internal) 3.5 inch hard drive bay, Desktop has one (internal) 3.5 inch hard drive bay, Small Form Factor has one 3.5 inch hard drive bay. All three variants have SATA connectors and if you are planning to swap the hard drive, it should work on either of the systems.
You can find the detailed information on installing the hard drive on Optiplex 380 from the service manual of the computer. You can find the link for service manual below. Select the link as per the variant.
- Dell Optiplex 380 Desktop Service Manual--Desktop: ftp://ftp.dell.com/Manuals/all-products/esuprt_desktop/esuprt_optiplex_desktop/optiplex-380_service%20manual_en-us.pdf
- Dell Optiplex 380 Desktop Service Manual-- Mini tower: ftp://ftp.dell.com/Manuals/all-products/esuprt_desktop/esuprt_optiplex_desktop/optiplex-380_service%20manual2_en-us.pdf
- Dell Optiplex 380 Service Manual--Small Form Factor: ftp://ftp.dell.com/Manuals/all-products/esuprt_desktop/esuprt_optiplex_desktop/optiplex-380_service%20manual3_en-us.pdf
Copy and paste the above links in the address bar of the browser and hit Enter.
You can also check the setup and features information tech-sheet from link: ftp://ftp.dell.com/Manuals/all-products/esuprt_desktop/esuprt_optiplex_desktop/optiplex-380_setup%20guide_en-us.pdf
Please reply for further clarifications.