I plan to do a clean install of W7 . How?

I plan to do a clean install on my brothers computer. I would like to prepare a bootable USB stick to accomplish this. Which tutorial should I use and which ISO should I write to the USB memory stick. He presently has Home Premium w/SPI on his computer.
He can't find his install disk. Short term memory is almost gone. Computer illiterate. Not much help.
Are all the numbers he needs to install and activate already on his computer? Which ones and where to find?
I wish to have all the material for this installation, with me, when I go to his home.

Hi blockie

I think you will need this tutorial by Brink

USB Windows 7 Installation Key Drive - Create

gregrocker said:

You don't say if this is factory preinstalled Win7 you're reinstalling.

If so follow the steps in Clean Reinstall OEM.

During the booted Custom install using the installer provided, delete all partitions and create new as you wish to format and begin install, or just click Next on the Unallocated Space to have the installer do it for you.

It is factory installed, so I guess an OEM iso onto a USB bootable memory stick would be the way to go.
However, I did a restore TO several months ago and turned auto updates back on (had it off for a few days due to errors each time it tried to update). The auto update worked without errors. Will wait a few more days. Hopefully, an install won't be necessary.
The computer in question belongs to my brother 20 miles away and I have a hookup with Teamviewer. I am wheelchair bound and we both are in our eighties. To top it off, he is not very computer literate. It's complicated.