If you are syspreping your windows partition in the XML file you can set it to expand disk to full. That is what we do for our images which only contains one image. The Settings Pass “specialize” then
<ExtendOSPartition>
<Extend>true</Extend>
</ExtendOSPartition>
Hope that helps others

Have you been able to upload images successfully before? Check the image file path in the web interface matches up with server path…Example /images/DellN7110 on server while the web interface is /images/Dell_N7110