No downloading and installing the updates during its installation

Disable the WLAN device inside your PC? That can be done in the Device Manager. If it is disabled, Windows won't be able to use it.

I do not know why you do not want to get the latest updates, but actually getting them is recommended. They will contain bugfixes and I don't know what, which you want to get. Also does the installer use your internet connection to get the newest versios of the drivers for your hardware so if you deactivate the internet connection you might unnecessarily run into hardware issues.

If you ask me, you should leave the internet connection enabled.

WhyMe said:

I doubt you'll find anything less drastic than pulling a cable or pushing a power button. It is about as quick and easy as you could get.

You can disable the WLAN device inside your PC.

However, I would not recommend doing so - see my above post!

the initial release of the windows build 10240 to the public is problematic hense the updates it downloads while it installs..... but as with any piece of software install at your own risk... have backups of previous operating system.... and backups of personal files