Deleting All Partitions and Clean install Windows 10

I have a top spec HP Envy DV6 i7 laptop which had Windows 7 on it then upgraded to windows 8 then Windows 10. I have noticed that recently the machine has become really sluggish and Cortana is not working not matter what I try.

I have decided to clean install Windows 10 which I have on a USB stick but before I do that I noticed I have 8 partitions

See below



What I want is to have just one partition and clean install Windows 10

So I would be extremely grateful if somebody could list the steps especially how do I boot Windows from USB drive.

How can I delete all the partitions and leave one

Many Thanks

Desmond

With the USB inserted, click the power icon in Windows 10 and select restart. Once the computer shutdowns, and right when it restarts, start pressing ESC. You should see a message something like Boot Paused or Startup Pause, you can stop pressing ESC when you see that (lower left corner of screen). Then you will probably press F9 to get into the boot device options.

Once it starts to boot from the USB flash drive, you will have to press a key to boot from USB, select your language and keyboard, on the next window select custom install.

Highlight each partition one at a time and click delete. WARNING: This will delete everything on the hard drive! Then click the unallocated space to install to and click next. Since Windows probably won't pick up a product key in bios, when setup asks you for a product key click "skip", "I don't have a product key", or "do this later". Then select the same version of Windows you had before, Home or Pro. You'll have to skip the product key two or three more times. When it's all done Windows 10 will activate itself when connected to the internet.

Make sure you have written down product keys for you previous Windows 7/8/8.1 - you can run showkey plus from this forum to display the product keys.

Showkey - Windows 10 Forums

Thanks Guys for your prompt replies much appreciated