I have a desktop computer with an extra HDD connected to it, and I have done "mark as spare" to it, but I don’t remember where I got to that setting. The HDD is no longer visible in Windows Explorer or Device Manager. IDK what I did… I want to revert this setting and take it back to normal. The HDD is empty, so data is in little danger, but its good space that I want to use.
Source: Windows Questions