Note that it will only download KB's that are in MS Security Bulletins, which are all the critical and important downloads; so you will still have to do a Windows Update afterwards to fetch the ordinary non-critical updates. This tool eliminates a critical gap in Windows installation. That is when you only have services packs installed but are missing all post service pack updates. An attacker can attack you while you are updating online and vulnerable. The tool is available from here: http://www.wsusoffline.net/. The site is in German and English.
So the plan is to run this tool on another PC to fetch the updates, and take the updates disc to the machine you are installing.
On the main screen, select the platforms which you want updates for, and checkmark Create ISO images 'per selected product and language', then click the Start button.
After it finishes, check the iso sub folder to locate the ISO image file. Note that this is a DVD image file. You need to right click on it and select 'Burn disc image'. Or you can use the free ImgBurn utility if you are not on Win 7 or Win 8.