So, there’s been some confusion around Windows Phone 7 and its support of removable/expandable storage. As is so often the case, this confusion comes from Microsoft: The company told me specifically (and repeatedly) that the OS would not support this. But it sort of does.
Here’s how it works.
Supported devices (not all Windows Phones will be expandable) will include a micro-SD card slot, which by Microsoft’s requirements must be placed under the battery cover (i.e. next to the actual battery) and not be externally accessible. That’s because this functionality isn’t designed to be something that is swapped out, used with a PC, or whatever. Instead, the micro-SD-based storage will work in tandem with whatever storage is available inside the device. So let’s say you get a device and it has 8 GB of storage internally plus an empty micro-SD slot. You could add a memory card (with 8 to 32 GB of storage) to dramatically expand the storage (to up to 40 GB).
What you can’t do is swap it out without hard resetting the device. That’s because the storage on the card and the internal storage is comingled, and the system makes no differentiation. There’s no way to know where something (an app, song, whatever) is stored, and if you do pop out the card, the phone will complain. And it won’t be readable on your PC, so you can’t use it to transfer content in either direction.
There are technical reasons for these limitations, but I can’t discuss them until my review can be published. (Sometime next week.) For now, let’s just say that Microsoft has cut an interesting compromise here by allowing users to expand the storage, and dramatically, on supported devices. But it’s not as free floating as, say, external memory card support on Android devices or whatever.
So, to put it accurately, Windows Phone does support expandable storage. But it does not support removable storage.
By the way, the Samsung Focus does provide a micro-SD slot. This is still very much the device I intend to buy.