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Last month I installed the Windows 8 Consumer Preview. I found out that my D disk (partition) automatically disappeared from my computer. I thought that was because Windows 8 hid the D partition. So, I decided to format the C disk and install Windows 7 again, but still I can't see my D disk,

I tried to defragment, hide/unhide the disk, also cmd » diskpart » list volume but still can't see any trail of my D disk.

But when I go to Device Manager and check Disk Drives » Volumes » Populate, I can see that there is:

  • Disk: Disk0
  • Type: basic
  • Status: online
  • Partition style: Master Boot Record (MBR)
  • Capacity: 305257MB
  • Unallocated space: 0 MB
  • Reserved space: 0 MB
  • Volumes only shows
    • C: 98006 MB.
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Not sure, but as far as I know Windows8 uses the GUID Partition Table instead of the old MSDOS MBR Partition Table Windows7 uses. Altering this table should render all previous partitions ununsable. A bit strange that they don't show in your Device Manager. –  Baarn May 6 '12 at 9:44
    
yea.but I already uninstall the windows8 and freshly installed windows 7, but still my D drive is not showing. :( –  Sb Sangpi May 6 '12 at 9:47
    
You have overwritten the MBR with a GPT by installing windows8, installing windows7 again installs a fresh MBR with no track of the old one. –  Baarn May 6 '12 at 9:51
    
when I upto the section where you are to select the partition to install the fresh windows7 but still in there I can't see my D drive partition. I already format the C drive and installed windows 7 last night. Are you suggesting to install windows 7 again? @walterMaier-Murdnelch thx –  Sb Sangpi May 6 '12 at 9:55
    
No, he's saying that by installing Windows 8 it most likely erased all signs of that partition and reinstalling Windows 7 is not likely to change matters. Rule No 1 for installing a new (and unreleased) operating system is to make sure you have backed up your important data. –  Mokubai May 6 '12 at 10:09
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3 Answers

Windows 8 does not, by default, use GPT disks nor does it convert existing disks to GPT. People often click through screens without realizing what they are doing and reading dialogs. I suspect you inadvertently did something to delete the D: partition. If you didn't, then I can only say Windows 8 is a "Consumer Preview" - a beta if you will. There can be circumstances, combinations of hardware and mouse clicks and keyboard keys pressed that cause weird things to happen. This is why you should NEVER install a beta operating system (or in my opinion, ANY beta software) on a system where you keep important data. Especially if you don't have a backup.

If diskpart and computer management are not displaying the old partition, I would consider it lost. You can try recovery software (GetDataBack is often referenced as being excellent) or accept that it's gone. If it was REALLY critical and you had no backup, then send the drive to a data recovery company. It's not cheap, but REALLY critical data is often worth the $400+ to recover it.

FYI, I'm writing this in IE10 on Win8 and I verified that this system, which was cleanly installed, did not install using a GPT disk type. I can also say that my laptop is multi-booting using VHDs (Win8 is installed in a VHD - NOT VM, but a VHD) and it did not convert the drive or I wouldn't be able to boot my system as I have a BIOS and not UEFI enabled system.

(Sorry, this is too long for a comment as far as answers goes, probably not what you were looking for).

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+1 Agree, just checked my recent install of W8, it made a basic mbr partition. –  Moab May 7 '12 at 3:36
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Instead of making a myriad of comments, I better write an answer.

I have not used windows8 myself, I can only guess what happened here.

Windows8 uses the so called GPT - GUID Partition Table - to specify which partitions are on the disk. Because this is a totally different concept than the old MBR - Master Boot Record - partition table from the MSDOS era even windows7 still used, the partitions created with either one of these tables are not compatible to the other one.

Well, in theory there should be not much difference between the partitions itself. They are defined by the filesystem they are using (mostly NTFS for Windows). But a new partition table overwrites the old one and thus all information of all earlier partitions will get lost. I have no idea why windows7 only shows a small percentage of your original disk space, it cannot even read the GPT, thus it should show you the whole disk as empty.

Before you do any further damage to that partition, you should try a recovery tool that looks at your drive for abandoned data, or maybe can even restore that partition. I cannot recommend you such tool, because I regularly backup my important files.

Even if it sounds mean, I hope you will learn two things:

  1. Never play around with (beta) operating systems if you have important files on the computer.

  2. And more important: Backup your (important) files.

If you happen to have a backup or were able to restore it, get a partitioning live CD and clean your drive.

As I said above, I never used windows8, everything I wrote is a wild guess. Maybe there is a simple solution to your problem, but I honestly don't think so. It basically costs Microsoft far more money to write a tool that can transfer some wrecked GPT to MBR and vice versa than putting up a warning that all data on the disk gets destroyed. And it is far more likely that you have just not read that warning and just clicked OK... and I wont even hold that against you, everybody does that ;)

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-1 Windows 8 does not by default, make and install itself on a GPT partition. Its just like W7, when installing you have to tell it which partition to install it on when there are multiple partitions available. –  Moab May 7 '12 at 3:37
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Use a Ubuntu live CD and boot the laptop using it. You will be able to see the lost partitions and files. You may not be able to access the drive where windows8 is installed.

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