I sometimes have to re-assign a drive letter when I can't see it in Explorer (but I can see it in the bios)
Like
@jefferz said, launch disk management (just type disk management into the run section if you can't find the setting in the control panel, and see if Windows had drive space that is unassigned).
The alternative (although you will lose your games, but keep your files/photos), is to launch windows installer and install a new installation on that drive (assuming installer can find it), but don't format the partition. You can then boot into Windows (either the old or new volume) and browse the file structure on the drive, and backup as needed).