I am not familiar with the Windows install since it is not officially supported and only produced for testing. But the "proper" Linux version does support offline installation. The problem you got is that without internet access you will really struggle to use Dataiku as you will be unable to create Python code environments or install any new Python packages, which is one of the Dataiku strengths. Having said that you can configure internal Python mirror repositories (ie Artifactory) if your company has one available.
If you don't have a Python mirror repository on your organisation and need to use Windows you could try the VirtualBox image which comes all preinstalled for you in a Linux VM: