The "HDD" (hard disk drive) label is a misnomer. It does refer to the SSD
. And a "HDD" size of 0 GB suggests SSD
To get the Mini 9 working again, you'll need a replacement SSD
. The Mini 9 only accepts special "Mini 9" SSDs. RunCores and 2nd gen SuperTalents are among the most well regarded Mini 9 SSDs. A used STEC (STEC makes the OEM SSDs) could be another choice.
You should be able to find one, used or new, on this site, or its sponsors, or eBay. Be aware that many major retailers don't stock Mini 9 SSDs anymore.
Instead of a replacement SSD
, you can run off a USB flash drive or USB hard drive or USB card reader. But as I stated earlier, it might not be easy to get Windows running on a USB storage device.
On other Minis, you can boot off an OS installed to an SD card in the onboard reader. But it has the same limitations as USB storage, and the onboard reader isn't bootable on the Mini 9, anyway.
Also, if you get a new SSD
, you'll need a way to install Windows on the new SSD
. The easiest way would be via a USB optical drive (maybe $40 for a slim DVD burner).