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Windows 7 defaults to assigning the letter C: to the primary partition if you let windows 7 handle a raw volume. However, assuming there are no optical/floppy drives, would it be possible to use DiskPart, create the partitions as necessary, and then assign say, letter A:? Would Windows install correctly and be usable?

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up vote 4 down vote accepted

No, Windows Vista and up always use C: as the system drive.

For example, if you have two partitions, one with XP and the second with 7 so that you can dual-boot XP and 7, you will see that when you boot into XP, it will still be on C: as before, but when you boot 7, it will also be on C:. What happens is that the system is mapped to C: while the partition that would have been C: will be mapped to something else.

The same is true if you dual-boot Vista and 7 or 7 and another copy of 7; each system will assign C: to its own boot-up partition and assign something else to the other partitions.

Further, A: and B: are special reserved letters that cannot be used as system drives, even in XP (though you can assign them to miscellaneous hard-drive partitions).

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So in DiskPart, would it even make sense to assign drive letters pre-installation? – Kevin Hua Jul 18 '12 at 2:15
As @Synetech said, no it would not. – imtheman Jul 18 '12 at 2:18
How are you running DiskPart? If you are running it in the System Repair console or pre-installation, then the letters will only be visible in that context and then Windows will re-assign the drive letters as necessary during the initialization phase of the installation. When you boot into Windows, it will see whatever letters you assigned regardless of what you assigned in other copies of Windows. – Synetech Jul 18 '12 at 2:19
I discovered this behavior of Windows 7 when I installed 7 as a dual-boot to XP. I was pleasantly surprised to see that I did not have to manually re-assign any drive letters because 7 already claimed C: for itself. :-) – Synetech Jul 18 '12 at 2:20
That's convenient, I can simplify my preinstallation script now =) – Kevin Hua Jul 18 '12 at 2:20

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