If you want to use your MicroSD card in any other device, don't stick it in a Microsoft smartphone.
Samsung is warning that the Windows Phone OS makes permanent changes to a card that can prevent it from being read, written to or formatted on any other device.
Samsung has warned that if you shove an MicroSD into the Focus, it must be considered a "permanent modification" as it will not be readable or writeable on any other device.
The software Imperium has warned of the permanent change. It seems that the operating system does something quirky to the card.
It might have something to do with the fact that Windows Phone 7 operating system treats the SD card as an integrated part of the phone.
In other phones the card is used to increase the memory available to the device at any time or to transfer files to other devices.
But there might be a little more to it than that. AT&T has warned punters that "Certified for Windows Phone 7" microSD cards should be used in Microsoft's mobile devices.
According to AT&T the Windows Phone platform "requires a certified high-speed microSD card for optimal performance."
This would be all well and good but Microsoft is yet to certify any cards and so far there is no sign when they will hit the shops.
This could be crucial as Microsoft support documents indicate that certification is a little more than working out how fast the microSD goes.
"Several other factors, such as the number of random read/write operations per second, play a role in determining how well an SD card performs with Windows Phone 7 devices," the page reads.
Expandability is pretty important to the phone as one of its advantages is that you can use it as a video player.
The weakness in MicroSSD certification could become a sticking point for sales. Although you would have to be fairly techie to see the problem.