Ahh, the wonders of the Card Readers and their relationships with Windows...
On most occasions, you're able to just unplug/replug the card in slightly different ways (like not all the way in, for example), and some weird combination of that will somehow fix the need of formatting, however there also is the rare occasion where an actual format into vFAT32 is necessary.
When this happens, your best bet is GParted Live. It's a free utility you download and boot your computer from that allows the formatting/reformatting of any drives in your computer (including SD/microSD cards) I must warn you that this is tricky to do, to say the least. If you've extensively tried the first option, and you know for a fact that it's hopeless, just send me a pm, and I'll help you through with GParted.