It took me a while but finally I unlocked my 32GB SD card after using it in my HD7 to upgrade it to 32GB, in my case the card proved to be un usable.
1• DFT HSPL/RSPL
Tools you need:
WP7 Update Cab Sender:
Download the following ROM
[ROM]XBmod HD7 V 1.01 Build 7720 [25/09] with Custom Cab
1) Boot phone with VOL- Pressed
2) Flash XBmod rom, HARD reset using Vol- and Vol+ pressed while powering on
3) boot to get started
4) extract and place "WP7 Update Cab Sender" folder in c:\
5) in C:\WP7 Update Cab Sender\if needed install this tool\ install correct ver of tool for your OS
6) place DEV_STORAGELOCK.cab in "c:\WP7 Update Cab Sender"
7) Confirm phone plugged in to USB and on get started screen.
8) close Zune and wait for process to stop (or you will get error on next step saying its still running)
9) run WP7 Update Cab Sender.bat in "c:\WP7 Update Cab Sender" click S
10) Once complete phone will show message saying update installed
11) click done on phone
12) complete phone initial setup skipping live ID
13) in your app list you will now show an app called storagelock, run it
14) when prompted answer yes to unlock SD card.
15) power off phone.
16) remove SD card
17) place in Windows PC
18) run CMD as Admin
19) run DiskPart
20) type list disk(this will show you your disks and the sizes so should be easy to see which number is your SD card)
21) type sel disk (then the number for you SDdisk) eg: sel disk 2
22) Being VERY sure you have the correct disk selected now type clean
23) now type cre part pri
24) if all went well remove sd card and reinsert and select it on Explorer
25) it will say its not formated and offer to format.
26) you now have full use of your SD card again
I hope this helps a few people.