image size growth

I have created 4 images, all an image of a previous image; baseimage.tib, baseimage2.tib, baseimage3.tib and baseimage4.tib. I made only tweaks to the OS in preperation of making this image the base image for all further images that would contain software for different test environments(there will be many such images, one for each test environment). For example, I turned of UAC, added a shortcut to a server folder on the desktop and turned on auto-logon. After each re-image the image size grew by 500 - 600 MB! OS bloat is bad enough in Windows 7! What is this overhead for each image? What can I do to minimize it?

When I image I do set the Compression setting to Maximum.

Help please,
Tim