What are GPT Protective volumes on Windows 8 and can they be recovered?

I have seen a few GPT Protective volumes now with Windows 8.x. These are default configurations where the users are very "un-savvy" and so they did not enable anything as far as additional security goes. I suspect that this may be some default bitlocker setting that MS or the mfg's (HP mainly so far) are setting?

When I have attempted to convert such volumes to MBR, it results in losing the data on the drive from what I can tell. I would very much like to understand precisely what is going on here so that I can work with these volumes better and also perhaps recover data as well.

Secondly, after understanding if this is something specific to Windows 8 (because I thought this may also be a normal "GPT" partition format also used in OS X, etc. up to now), has anyone seen any applications or utilities that will facilitate recovery of a volume that has been converted to mbr or had other operations performed? I have not seen any success with Stellar Phoenix, for example.

It's not 100% clear to what you're referring, but the term "protective" in the context of GPT generally refers to the "protective MBR" or "protective partition," which is basically an ordinary MBR with a single partition of type 0xEE that spans the entire disk (or as much of it as is valid for MBR, in the case of a disk with more than 2^32 sectors). The intent of the protective MBR is to keep GPT-unaware tools from messing with the disk, since the real partitions are defined elsewhere. If somebody were to delete the protective partition using a GPT-unaware tool, the result would be that most GPT-aware tools (including both partitioning programs and OSes) would identify the disk as being completely unpartitioned, although some would detect the remaining GPT data and offer a recovery option. In any event, deleting the protective partition on a GPT disk is a Bad Idea (unless of course you want to completely wipe the disk). Note that none of this has anything to do with Windows, except insofar as Windows Vista and later understand GPT, and most computers that ship with Windows 8 use GPT on their boot disks. Mac OS X, Linux, FreeBSD, and other OSes also understand GPT.

If you've trashed a disk by deleting its protective MBR, try using my GPT fdisk (gdisk) utility on it. gdisk is one of the partitioning tools that looks for GPT data and will help you recover it in this sort of situation. If the disk has been further damaged by wiping the GPT data, tools like TestDisk can often create a fresh partition table based on filesystem data that they can detect.

For more on the GPT data structures, read the Wikipedia page on GPT.