Don’t put your MicroSD cards into Windows Phones. According to Samsung, doing so is a ‘permanent modification’ to the card, and it can no longer be used in other devices.
And Microsoft backs this up.  They state here [microsoft.com], that is happening more clearly.
When the operating system integrates the SD card with your phone:
- It reformats the SD card.
- It creates a single file system that spans the internal storage and the SD card.
- It locks the card to the phone with an automatically generated key.
From this point on, the phone’s operating system uses all of the available memory as a single storage space for storing applications and data. The phone will stop working properly if you remove the SD card, and the SD card cannot be read by another phone, device, or PC.
It’s not just one data point from some casual observer. The manufacturer of the operating system states quite clearly that this is the expected behavior.
Why? Â Why use SD memory, if it’s not intended to be removed?
Some Windows Phone 7 devices include a Secure Digital (SD) card slot underneath the battery cover. If you buy a Windows Phone 7 device that includes an SD card slot, you should be aware of several important differences from other devices that use SD cards:
- The SD card slot in your phone is intended to be used only by the Original Equipment Manufacturer (OEM) that built your phone and your Mobile Operator (MO). These partners can add an SD card to this slot to expand the amount of storage on your phone.
- To help ensure a great user experience, Microsoft has performed exhaustive testing to determine which SD cards perform well with Windows Phone 7 devices. Microsoft has worked closely with OEMs and MOs to ensure that they only add these cards to Windows Phone 7 devices.
- You should not remove the SD card in your phone or add a new one because your Windows Phone 7 device might not work properly. Existing data on the phone will be lost, and the SD card in your phone can’t be used in other Windows Phones, PCs, or other devices.
So it appears that the SD slot, is intended to boost the memory in the device when sold. Â Not as a “Floppy” or removable storage.
