How to restore an SD card's full capacity

A reader wrote in to PC Advisor for help in restoring his SD card's capacity when his 4GB card showed only 1GB available. Here's how we fixed his problem. See also: How to recover files from a corrupt SD card

Q "My SD card is showing a capacity of 1GB when it should be 4GB. Can I fix it or should I just throw it away? I’m using a USB SD card reader and when I plug in my card it shows up as a drive, but Windows tells me it needs to be formatted before I can use it. If I go ahead with the format, the available size is only 1GB when I know it’s a 4GB card. This led me to go to the Disk Management tool in Windows 8 and look at the drive there. Here I found what looked like several partitions, some of which I have managed to remove, but many of which stubbornly remain. How can I completely erase my card and get back the full 4GB capacity?"

You SD card does indeed look a bit of a mess, so a low-level format is probably the best solution for you. You’ve already stated that you’ve been trying to format the card, so we’ll assume there’s nothing on it you’re not prepared to delete. See also: How to get more storage on Android

A low-level format will completely erase your card without regard for any partitions or volumes which may exist. This principle also applies to other types of storage media, such as hard drives and SSDs. See also: How to fix Android's 'insufficient storage available' message

To perform the low-level format, you can use a free tool such as HDD LLF Low Level Format Tool from Hddguru.com (tinyurl.com/3jjcrf4). The free version of this tool is speed-limited to a maximum of 180GB per hour, but seeing as you’re only formatting a 4GB SD card this won’t be a problem. If you ever need to low-level format a 1TB drive, you may wish to pay $3.30 (£1.95) for a home use version without the speed limit.

Be absolutely sure to select the correct drive before proceeding with the format, as it will irretrievably delete all the data on the selected drive. Choose your main hard drive by mistake and you’ll regret it. Once the low-level format is complete, you should be able to reformat your card and enjoy the full 4GB capacity once more.

In the case of troublesome SSDs, you’ll often find manufacturer’s offer software that will let you perform a secure erase function, zeroing out all locations of the SSD including those which cannot normally be accessed by computer software. This works by sending a Secure Erase command to the onboard controller of the SSD, effectively commanding the SSD to erase itself.

If your manufacturer hasn’t provided a utility to do this, you can use a free tool called HDDErase which can be installed on to a bootable USB drive. It can be downloaded from the author’s website here – tinyurl.com/qf234gz. However, this tool is extremely fussy about exactly how you configure your drives and your PC BIOS, and can prove frustrating to use.

Parted Magic (partedmagic.com) is sadly no-longer free, but for just $4.99 (£2.95) it provides a graphical interface and a huge selection of storage-related tools including an SSD Secure Erase utility.

Still stuck? Get free tech advice in our Tech Help forum.

(See also: Recover deleted files for free: recover lost data.)