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I started on Ubuntu and have had the first considerable error. I have an HP Pavilion DV6 Core i7. I had installed Windows 7 and I decided to also install Ubuntu using USB.

My first attempt was to install Ubuntu 11.10 following the instructions of the official Ubuntu website. When loading the pendrive, my PC got stuck at the main menu of Ubuntu, so after searching, I found that could be due to a problem with my AMD Radeon graphics card (or not), but I decided to change.

Then I used Ubuntu 10.4. This could happen from the start menu I use to get into Ubuntu live. There I decided to install it because I liked it and I need to develop with Google TV (in Windows that's not possible).

And I fail in the partitions section. I tried to follow the instructions on this page (Spanish).

There were things that changed a bit, so I improvised. I took the Windows partition of 700000MB and went to 600000MB, leaving 100GB free to install Linux there. The error was to set it to ext3 (it was ntfs). I thought the new 100gb partition will be set to ext3, and windows partition will stuck at ntfs system, but not.

Total I ran out to boot Windows, and above I can not install Ubuntu on the 100GB free.

Is there any easy way to convert back to NTFS Windows and not lose data?

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If you did not format (often called "creating a file system" in the *nix world; it's been a while since I ran Ubuntu, so I am not sure if that's the exact terminology they use) the partition, chances are pretty good that you can boot into a Linux recovery console and use a tool such as fdisk to simply reset the partition type to NTFS/HPFS. That would, in theory and assuming that nothing else was written to the disk (or that the resize itself was successful, which is doubtful if you both shrunk the partition and set a new partition type, which would almost certainly follow from the file system change), allow Windows to find it again in much the same way it did before. Booting from the Windows installation CD and performing a repair may also accomplish this, but I'm not certain.

However, my guess is that the installer also formatted the partition using the new file system, in which case critical NTFS data structures (boot sector pointers, parts of the MFT, etc.) as well as user data were very likely damaged or even outright overwritten by their ext3 counterparts. If that's the case, you should expect that at the very least some of the data on that partition is now irrecoverably lost. There are quite a few data recovery tools out there to work with NTFS partitions, though, which will analyze the on-disk data and structures in an attempt to dig out as much useful data as possible. Note that generally, for that to work, you will need a second disk of at least the same size to hold whatever is found and salvageable, and it is critically important that you do not cause any further writes to the original disk before you at least have a full disk image to feed such tools. Data recovery tools can be had both at a cost and for free; you may want to search both here as well as over on Photo.SE, where questions involving such tools come up occasionally.

In honesty, this is why one should always make a full backup before performing such a potentially destructive operation as repartitioning and formatting. The tools today are usually well enough developed and tested that it's rarely a problem, but if anything goes wrong (software bug, human error, power failure in the middle of a long-running operation, whatever) then the consequences can be anything from an extra file system check needed on reboot to outright obliteration of all data on the physical medium.

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Ok. So I have to try to use fdisk to reset the partition to NTFS/HPFS. I didn't know how to do that. I will find it. Thank you very much. And yes, a backup have been ok :S – Huèspal Mar 6 '12 at 16:17
I certainly can't guarantee that it will work (it depends on what exactly happened), but it's a relatively safe thing to try as long as you make no other changes. I would still strongly recommend making a bit-by-bit image of the drive before trying anything if you aren't absolutely sure about what you are doing, but of course that requires somewhere to store the some 700 GB. – Michael Kjörling Mar 7 '12 at 10:22

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