[HD2 Android SD Development] bromerrill:
Finally: Dual Boot Using the single card method.

After many hours struggling with this process I succeeded in formatting the SD card for dual boot. Considerations 1) First, you need an SD card which is recognised by WP7 and Android. I tried three different ones in this process- a Transcend 2gb; a SanDisk 16gb; and an 8gb Kingston- all different speed classes, and they all worked. I ended up using the 8gb card with a~ 4gb WP7 partition and the remainder for Android 2) You need a card reader which does not give a write protected error- the card reader has a lot to do with whether you can read the SD card after you install WP7 and it formats the card 3) You need the Mini Tool Partition Wizard for the last step 4) You need to be able to see your SD card in the partitioning apps (I had a lot of problems with this on Win7 32 bit, but it went much better on Win7 64 bit- I also found that I had to repeat the reset WP7 process twice or more after every resizing before my SD card was visible in Win7).

I used HSPL4 (HSPL3 was corrupt for me), Magldr 1.13, the DFT Ultrafruit build, and the CyanogenMod7 from the YouTube tutorial by 96edwsMobile.

So after installing Ultrafruit, which was fairly simple, using the 8gb card I had a 200mb Fat16 partition first (on the left side of the Partition Master display) and a ~7.6bgb partition in second place on the right.

For me the crucial steps were to do the reset in WP7 and stop at the Magldr menu without turning off the phone or doing any navigation, take out the SD card and change only the WP7 partition (which by default is unformatted) by deleting that partition (what you really are doing is resizing it, but resizing as unallocated and creating the resized partitition as Unformatted in the size you need to make that partition larger than the Android partition you are going to create). When you do the delete you get the 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 which will be larger than Android partition.

Then you put the card back into the phone and continue the boot into WP7 process where you stopped. WP7 will then reread the partition size and recreate its file structure in the resized partition. You can do this process any number of times to resize the partition, as I did, to end up with the proper size as long as you first start the process with the reset phone step in WP7.

I recommend resetting the phone once or twice more without changing anything if you can't read the sd card.

When WP7 is happy with the resized partitions and you can read the sd card in the card reader, do the reset WP7 process again and stop at the Magldr menu (do not turn off the phone or navigate anywhere else), take out the sd card, put it in the PC and use Partition Master to change only the 200mb Fat16 partition. Select that partition, resizing it to fill up all the remaining unallocated space and reformatting it as Fat32 with a cluster size of 32 or 64 kb if possible.

After you do that, put the sd card back in the phone, boot into WP7 from the Magldr menu and check that WP7 is still happy with the new, resized partition for Android. If it boots and gives you the "get started" option it should be good to go.

Then you can turn off the phone completely, take out the sd card, and in windows explorer transfer the Android files into the "Android" folder you create in the Fat32 partition. You have to be sure to have the proper rootfs.img and startup.txt files (Google it).

Then, after you have all the files on the card you have to use the MiniTool Partition Wizard as the last step to prepare your card by changing the Fat32 partition to Primary.

I used the files from 96edwsMobile (Copes SD Gingerbread CM7 04-02-2011) which already were edited in the download package so I did not have to edit anything except to copy those 2 files mentioned from the SDMAGLDR folder to the Android folder, overwriting those there already. (You do not copy the SDMAGLDR to the sd card).

After I loaded the files to the Android folder I replaced the card in the phone and booted up into the Magldr menu, stopping there and selecting "10.services", "1.Boot settings", "1.Boot source", "1 Android From Sd", backing into the main menu and "2 Boot AD sd". You will also have to select the "Android" option at first bootup in Magldr.

The first bootup took a long time, like 8-10 minutes, the screen reading HTC and no other activity showing. Then I was in. Later you change the Magldr menu to "2 Always Menu" if you want to select your OS at bootup.

I am not much excited about the CM7 build. I had installed the Energy_2.8.2012.SensationXL build to NAND prior to setting up the dual boot, and I like it a lot. If anyone knows where to get the SD version I would appreciate a PM or a posting.

You have to be very careful to do each step in the order mentioned to achieve success. My OS'es seem to be running smooth as of now. Hope this adds clarity to the single sd card method.