Do you know a way to do it without the nook and just on a computer?
1. Remove SD card from nook
2. Turn on nook, boot into stock
3. Put SD card in nook
4. Go to Settings>My Device>Format SD Card
No PC is required
Well first you need your computer to have a micro SD card reader. If it has this, then right-click card in My Computer and format. easy as pie. If it has no reader then you can't do it.