I have a 2TB hard drive with 2 partitions on it, one a C drive (500GB) for WinXP and another for extra space (1.5TB).

I have a Win7 Pro install DVD and I have formatted that C drive via the DVD; it is now a blank "Primary" partition.

I attempted to go through the Win7 setup and install it on that partition, but it's giving me an error:

Setup unable to create new system partition or locate existing system partition. See setup log files for more info

Googling around leads me to believe the entire drive has to be "cleaned" (diskpart) but that would wipe the entire other non-OS partition and I need to keep that data. The exact quote that I found:


That's because the drive was partitioned prior to the Win-7 install. What you want to do, to have Win-7 install the 100MB MS hidden system reserved partition before the OS partition, is to start over as a clean installation. Choose Custom (Advanced), then when you come to the 'where do you want to install windows?' Delete all the partitions on this 250GB drive.

Also not have any other HDD connected, and if possibly make the USB drive folder Read Only, so the MS reserved partition doesn't get placed on it. Do you by chance have the DVD installation disk if need be?

Give that a try, and if all goes well, in Disk Management, you will see a 'hidden' MS reserved 100MB system partition, followed by your Win-7 OS, boot, crash dump, pagefile partition.

I don't want to wipe out the entire 1.5TB partition, I simply want to install Win7 on the other 500GB partition. How can I install Win7 on this blank partition without losing data on the other partition?

Or where is the setup log located?


First things first, disconnect all removable drives. Next, if you booted the CD by temporarily changing the boot order via the F10/F12 boot device menu (keyboard shortcut is specific to your motherboard manufacturer/model), instead go into the BIOS and change the boot order so that the DVD drive is accessed before the HDD.

Now reboot and try installing Windows 7. If it doesn't work, try using a USB-based install instead (you can transfer the DVD to USB directly using WinToFlash (or Microsoft's own Windows 7 USB/DVD download tool, but you'd need to create an ISO from the disc first).

Next thing to try would be deleting the first partition via the Windows 7 Setup and creating it again, then attempting to install into it as before.

P.S. I hope you didn't have to load any drivers to access the drive during WinXP Setup? Lack of those drivers could also cause this sort of error.

  • I used a USB to load the install files to the 1.5TB partition and executed the installer from there during boot. – Zeno Oct 24 '12 at 3:30

Windows 7 requires 2 partitions (100MB system reserved and the partition for OS) and I don't think Windows can change the partition table without destroying existing partitions. There are advanced partitioning software out there that might be able to rewrite the tables and keep all of the data intact. Try this software http://www.acronis.com/homecomputing/products/diskdirector/

  • What exactly would I be doing with that software? – Zeno Oct 22 '12 at 13:43
  • @Zeno - Do a Google search. – Ramhound Oct 22 '12 at 13:47
  • @Yamaha32088: No, Windows creates the 100 MB System Reserved partition only if the disk is not already pre-partitioned. If it is, it simply installs into the partition you specify, since Setup won't bother to move your data and create free space at the beginning for the 100 MB partition. – Karan Oct 22 '12 at 18:40

You could use a linux live cd and backup your data to another location, before cleaning the entire disk and installing the OS.

  • It's 1.5TB of data, I don't have space elsewhere for that. – Zeno Oct 22 '12 at 13:42
  • @Zeno - You need to backup your data before you do anything. In order to install Windows 7 you need to format the partition Windows 7 is going to be installed on. – Ramhound Oct 22 '12 at 13:45
  • @Ramhound: "In order to install Windows 7 you need to format the partition Windows 7 is going to be installed on." - Didn't he mention that he did that already? – Karan Oct 22 '12 at 18:38

before you install click on "repair my computer". cancel the startup repair menu go to advanced options. open cmd prompt. do a full format, not quick, on that partition with diskpart. then try again.

the log files are viewable on the PE x:\ partition.

  • Can you specify how a full format will be advantageous as opposed to a quick format, and how it would solve this problem? I never bother with a full format, and never had any problems all these years. – Karan Oct 22 '12 at 18:42
  • The difference between quick and full is a scan for bad sectors. Full format scans for bad sectors marks them so they arent used. If there is a sector that is bad where the OS is trying to write he may have a problem. – BroScience Oct 23 '12 at 13:36
  • So you're saying the error could be due to bad sectors? – Karan Oct 23 '12 at 13:38

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