Restoring a SD card after using it to root a device

I recently purchased the Nook Touch reading device.

I rooted it using the instructions on nookdevs.com

Rooting included using win32diskimager to somehow transfer an .img file onto the card.

Rooting is now completed and as far as I can tell, I don't need to keep the files used on the SD card, which has been reduced from a 3.5 GB or so unit to a 75 MB unit.

Is there a simple way for me to somehow reformat the SD card to its original state or at least 3.5 GB. I cannot simply format it.

I've had this happen before. This happens when you clone an image (like an ISO or IMG file) to a disk or flash card that has a smaller capacity than the disk/card. I've had this happen when making bootable Linux USB disks from a live CD image.

The easiest way to fix it in Windows is to use HP's Disk Storage Formatting Tool. It lets you format the drive and choose the capacity, all the way up to the maximum.

When I first ran into this issue I had to use this program to restore an 8 GB USB stick. Windows detected its maximum capacity as 250 MB even if I tried to format it through Windows.

Using diskpart (as described here) worked for me.

In a nutshell:

diskpart

list disk

select disk (disk no)

clean

create partition primary

You need to be very careful at the second and third steps to make sure you've chosen the correct disk.

Windows Disk Management will do just fine. Right-Click on My Computer > Manage > Disk Management. Find the drive for your [micro] SD card, right click on the partition(s) and delete it/them. Afterwards, you can right click and choose format, which will let you use the full size of the card. (I've done this many times in the same situation as you, where I had to use the disk imager which created smaller partitions than the capacity of the drive).

"Disk Management" on my Windows 7 PC doesn't allow me to delete the SD partition.

I use my Canon PowerShot S100 photocamera to do it. Use the "low level format" option.