I was formatting one my PCs to perform testing.

The first partition seems to be EFI or something that I shouldn't touch.

When creating a partition, Windows 7 automatically creates a 100MB blank partition before the partition that it will be installed on (which is then the 3rd partition). Why is this and what is this for?

With Windows XP, I can create a partition and IIRC, sometimes I may have a blank partition at the end which is small (approx. 8MB).

Can someone explain why Windows 7 creates a 100MB partition before the partition that it will be installed on? And why at other times there will be a tiny partition at the end? (NOTE I only care about the 100MB before my main partition).

3 Answers 3


The 100MB partition you're seeing is used by Windows 7 for:

You can prevent it from being created during setup by following these instructions at WinMatrix.

Note: they talk about a 200MB partition. Pre-RC1, Windows 7 used 200MB. But as of RC1, the Windows team reduced it to 100MB. Alternatively, you can pre-format and partition the drive before installing Windows 7, and the recovery information will be placed in your installation drive.


The 8MB is reserved for dynamic disk conversion


Not sure what the 100MB partition has to do with EFI, unless you're installing it with Bootcamp on a Mac, in which case there is a 100MB partition that is used for BIOS emulation I believe.

edit: With a Vanilla Win7 install I believe it puts the boot files there if it was previously unpartitioned. I can't find documentation from MS right now, but maybe someone else can.


If you don't like it, you can always partition manually using DISKPART or other utilities. You can bring up a command prompt to run DISKPART right in the Windows 7 setup environment by pressing Shift+F10.

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