Well, the question is simple.If you want to install, you must configure 11Gb on disk space. If not, the installation begin, but after the installation files expanding, the virtual machine enter in a spiral of error and restart...has somebody tested this way?

For any OS I have used and tested on ESX Server (Linux, Windows, or otherwise), I always give a minimum 25GB of disk space so that I won't run into any issues related to storage. It seems to me that 11GB is kind of small for Win7.