[HD2 Windows Phone 7 Development] Whatdoyaknow:
This is how I do it:

(I notice the colors mentioned have now changed, but you get the idea)

1. Put your sd card inside the hd2 and power on.

2. Go to about screen, in settings, and reset your device. Let it reset and boot to WP7 again. While booting to WP7, it'll create the partitions it needs, so this is important. After you have gone through the setup wizard, go to about screen and reset your device again.

3. When it has booted into magldr screen, remove the sd card and insert into pc. (make sure that magldr is shown and stays there at bootup, otherwise it'll boot straight into wp7 without sd card and that is not what we want.

4. Using EASEUS Partition Master Edition, you'll see two partitions. A whopping 200mb of fat16 partition and the other is unformatted.

Now right click on the unformatted partition and click delete. After that, click apply. Now you have unallocated space.

Right click on the unallocated space and select create. Set parameters to logical and unformatted and size the partition. This will be your WP7 partition, so decide how much you want to allocate to it, this is permanent, no changes afterwards can be made. Also, make sure you move it to the end of the sd card in the same 'create' window. Hit apply. IMPORTANT When using this method make sure that the wp7 "unformatted partition" is larger than the Android partition otherwise the wp7 "unformatted partition" will move in 2nd place and you will not be able to resize the fat 16 / android partition.

6. You now have a green fat16 partition to the left, some unallocated grey portion in the middle and your WP7 partition in modern turqoise colour on the far right. Agreed? Now remove the sd card from PC and insert in HD2.

7. After you have inserted the sd card, let it boot into WP7. Remember what your last action was when you were still in WP7? Yes, you pressed reset, so the device actually thinks he is still resetting the device. He might do it too, but just go through the setup wizard again.

8. Go to about screen and verify your storage. Don't look strange if when the storage has a different of about 1Gb, this is swallowed by WP7 for system stuff etc. Are you happy with the progress so far? Then power down your device and remove the sd card. Allow the HD2 to fully powered down as sometimes the screen is pitch black, but the device is still turning off.

9. Insert the sd card in pc and, using EASUS right click on the green fat 16 partition and select resize/move. Now fill up the rest of the unallocated space and hit apply. This is your android partition.

10. Format the sd android partition (not the whole sd card!) using EASUS to FAT32 using 32 or 64 kb cluster size and put an android build onto it and test.

11. IMPORTANT You need to convert the wp7 unformatted partition to primary for the sd android to see the sd card Use minitool partition wizard to do this. Right click on your WP7 unformatted partition and select modify and then click on set as primary and hit apply. Here is the link for minitool:

http://xdaforums.com/showpost.php?p=10887494&postcount=372

Modified version originally from

http://xdaforums.com/showpost.php?p=15626733&postcount=2