I have been able to re-install the 32GB microSD card from my dead Focus into my replacement Focus. The card was formatted on install as with a new card and I had to re-install everything, but apps and my 5700-track Zune collection have now been re-loaded into the 36.9GB install. I simply removed the card from the dead unit and inserted it into the new phone's card slot, tried the 3-button card-install instructions in the user guide, and it worked on the first try. Four updates, including Mango, also installed without a hitch. I installed the card after the first two updates because that's the point at which it worked for me last year.
So, although the user guide warns you that a WP-formatted card will not be usable for other applications, it does work for a WP re-install.
Ensure that you have sufficient free space on your hard drive prior to connecting your phone; otherwise, the update installation(s) may stall on a "checking to see if you have enough space to do a backup" message. I learned this the first time and freed 44GB of space.
So, although the user guide warns you that a WP-formatted card will not be usable for other applications, it does work for a WP re-install.
Ensure that you have sufficient free space on your hard drive prior to connecting your phone; otherwise, the update installation(s) may stall on a "checking to see if you have enough space to do a backup" message. I learned this the first time and freed 44GB of space.