Additional partition being created when installing Windows 7

Solution 1:

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

• WinRE (Windows Recovery Environment)
• BitLocker.

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.

Solution 2:

The 8MB is reserved for dynamic disk conversion

http://support.microsoft.com/default.aspx?scid=kb;en-us;225822

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.