I always wipe my machines and do a clean install to get rid of the crapware so many OEMs put on their machines.
They way I do it is.
1) Ensure I have the correct copy of Windows either on USB or DVD (
wintoflash is great for this.)
2) Download all the drivers for the OEM website.
3) Backup the current state of the machine (Windows Backup/Acronis True Image/Norton Ghost) so that if I f**k up I can just restore and try again. Miss out this step and things WILL go wrong, you have been warned!
4) Boot from the USB/DVD and do a custom install, including deleting the current partition(s).
5) Install any basic drivers needed to access internet. (Usually just ethernet card)
6) Allow windows update to fully patch the machine, sometimes takes two or three updates depending on how old the OS is.
7) Install any other drivers needed (display/sound).
8) Backup my nice clean version of the machine.
9) Install any other software need.
10) Have fun using my new computer.