If you want to change SD card on your Windows 7 Phone you might experience some issues with it. If you decide to switch your SD card, you’ll have to perform a hard reset in order for you to use it. According to Microsoft, Windows Phone 7 is using high performance SD cards that work differently than other SD cards. When your phone is built, internal storage space and SD card space are combined into a single storage unit and Windows Phone 7 recognises them that way.
Microsoft warns that you shouldn’t remove your SD card, because it may lead to loss of data. In addition, SD card from Windows Phone 7 cannot be used on other phones.