Are any of the "unallocated" drives larger than 2 TB? Older computers don't natively recognize larger drives, and the only way to use them is to install a driver (i.e., you cannot simply upgrade the BIOS). If this fits your situation, then either you or the company that made the computer probably installed this in your Win7 configuration. You'll simply need to install that same driver for your Win8 partition.

It's not that old a machine.. i7, 16 gig ram, with an ASUS maximus v extreme mobo.

Drives are set for ahci. Some are MBR and some are GPT. Win 8 is seeing one mbr SSD and one 3TB GPT drive. All the other (MBR) drives are showing as unformatted.

That means that Windows 8 not reading the very small data file on each hard drive that Windows 7 installed. Maybe, just guessing.
JJK

Drives are set for ahci.My previous post was based on something I learned from actual experience. Your comment that all drives are set for AHCI reminds me of another problem I had not that many months ago. The short version of a long story is that I found that to use AHCI, I not only had to change this for the drive in the BIOS (you don't have a BIOS, but I assume there is some setup parameters you still set), but I also had to change the driver for that drive. Since it involved a boot drive, it was actually a difficult thing to do because you usually do this when you install Windows.

So, the AHCI driver for the problem drives would be another thing to check.

"(you don't have a BIOS, but I assume there is some setup parameters you still set),"

I'm not sure why you assume I don't have a BIOS or access to it? Maybe I'm misunderstanding, but this board has dual BIOS. At any rate I don't think that's the issue though. I've been through the bios settings and everything looks fine. Windows 8 is indeed seeing the drives. They are there so I don't think bios is the issue. It's even showing the various partitions and logical drives on each of the physical drives. It's merely showing the drives as unformatted. Meanwhile, when I boot back to windows 7 everything is back to normal and all the drives and data is there.

Could there be some kind of security issue going on between 7 and 8?

"

Small data file?

Every hard drive sets a very small partition for "secret data" for that drive in addition to the main partition. It is pretty small maybe about 9 megs. So when you format you are only formatting the main partition. I have no idea how the secret data is compiled. If you "double 00" the drive then you start totally clean. Anyway that's what my guru says. He always double zeros the drives for a clean install no matter what. But this problem might be solved by something much simpler that is beyond my knowledge base.
JJK

This is just plain strange and I can't figure it out.

I've backed up all my data on the drives in question, then I boot to windows 8 and format the drive (NTFS). The drive then shows up fine in windows 8.

I boot back to windows 7 it states there are errors on the drive (just formatted by windows 8) and it corrects them. The drive then shows up in windows 7 fine.

I boot back to windows 8 and the drive reads "unallocated" again.... so I reformat the drive... and this all becomes a circle that goes around again.

Windows 7 and 8 are clearly looking at this drive very differently.

Any clues at all??

I come back to AHCI.

You stated that you are using AHCI in Win7 to access the drive(s). That requires a setting in the BIOS and it requires a Windows driver. This driver is usually installed at the time you install Windows. If you did not install it, any drive set up for AHCI will not work.

I think -- although I am not certain -- that you might get the behavior you describe. You mentioned you have some sort of dual BIOS. I don't know how that works, but if one is associated with Win7 and the other with Win8, then you need to have AHCI set for both. In addition, you must have the AHCI driver installed for that disk drive, for both operating systems.

You might try doing some searches over at Tom's Hardware. That site has a lot more posts about this sort of thing.

My guru buddy says to make sure both your operating systems are 32 bit or 64 bit and not mixed, in other words you cannot dual boot a 32 bit system and a 64 bit system unless you use separate drives for each one. Then it's a waste of time. Just another thing to check.
JJK

"You stated that you are using AHCI in Win7 to access the drive(s). That requires a setting in the BIOS and it requires a Windows driver. This driver is usually installed at the time you install Windows. If you did not install it, any drive set up for AHCI will not work. "

That would make sense if all drives are not being read... which is not the case. There are two drives which both 7 an 8 can read. One is mbr (SSD) and the other is a 3TB gpt. That's what makes this so baffling. If no drives worked then you may be able to blame it on the lack of a driver.

Now there is one difference I have noticed in drivers though.... The RAID controller driver used for windows 7 and windows 8 are not the same. Apparently the Asmedia controller used in windows 7 is not compatible with windows 8 so they're using intel 7 series controller. That's the only thing I can think of that's different though.

"My guru buddy says to make sure both your operating systems are 32 bit or 64 bit and not mixed, in other words you cannot dual boot a 32 bit system and a 64 bit system unless you use separate drives for each one. Then it's a waste of time. Just another thing to check."

Thanks.
Both are 64