The tale of expandable storage on Windows Phone 7 is certainly convoluted. We know that they take them, but we also know it's very finicky. When we met with Samsung on October 11th, they told us it wa a permanent change to the device and that once you insert that card, that's it, there's no going back. We wrote back then:

Basically you can any size card you like, but you can't remove it without hard-resetting the phone and it's not clear that the card would be re-usable if you do remove it. So essentially, if you add a 16GB or 32GB card, that's it, you got your shot.

Engadget recently confirmed this, noting that the cards were unusable and cannot even be reformatted. Going further, AT&T changed their tune saying don't add any memory to the Focus, not yet at least. The problem is waiting on specific cards that were "certified" to be used on our devices, cards that met certain performance standards.

Today, Samsung moved very quickly (1 week, not bad) to the controversy and said that Sandisk 8GB Class 2 cards will work on our devices. The bad news is that their support doesn't seem to know that the Focus only has 8GB on board, not 16GB. Going further, this sounds kind of iffy at best. While we don't doubt the 8GB Class 2 cards will work, the whole "officially certified" thing sounds like it is still weeks away from happening.

Hi, actually the Samsung Focus has a 16GB internal memory and expandable up to 32GB. So you can insert a 32GB micro SD card on this device. However there are certain limitations when it comes to the micro SD card. Compatible micro SD cards will be branded as “Windows Phone 7 Compatible” on the packaging. Approved cards can be obtained from the manufacturer or carrier. (The SanDisk 8GB class 2 micro SD card has been certified.) Many commercially available retail micro SD cards are not approved for use in Windows Phone 7. Use of unapproved cards may cause performance degradation or device instability, including unexpected reset and loss of user data. A micro SD card class is not an indication of meeting Windows Phone 7 requirements.

If you want data based on user feedback, MobilityDigest did a whole list of cards that supposedly work and don't work, which we reprint after the break.

Sources: Samsung Support, Engadget, MobileTechWorld, MobilityDigest

Confirmed Working(Data remains after soft reset):

  • Kingston 4GB Class 4
  • Kingston 8GB Class 4
  • Kingston 32GB Class 4
  • Microcenter 16GB Class 2
  • SanDisk 8 GB Class 2
  • SanDisk 16GB Class 2
  • SanDisk 16 GB Class 6

Currently Unstable/Unsure:

  • SanDisk 32 GB Class 2 (Confirmed working by Rok17 )

Confirmed Not Working(Data gone after soft reset):

  • A-Data 4GB Class 6
  • A-Data 16GB Class 6
  • Lexar 16GB Class 6
  • Transcend 8GB Class 6
  • Transcend 16GB Class 6
Confirmed Working(Data remains after soft reset):
Kingston
Kingston 4GB Class 4
Kingston 8GB Class 4
Kingston 32GB Class 4
Microcenter
Microcenter 16GB Class 2
SanDisk
SanDisk 8 GB Class 2
SanDisk 16GB Class 2
SanDisk 16 GB Class 6
Currently Unstable/Unsure:
SanDisk 32 GB Class 2
Confirmed Not Working(Data gone after soft reset):
A-Data
A-Data 4GB Class 6
A-Data 16GB Class 6
Lexar
Lexar 16GB Class 6
Transcend
Transcend 8GB Class 6
Transcend 16GB Class 6