installation - Reinstall Windows 8 in a Dual Boot Setup?

I am currently using Lubuntu in tandem with Windows 8 in a dual boot setup. Windows 8 is getting sluggish, so I want to do a clean install of it. In addition, I want to go from Lubuntu to Xubuntu (my laptop is more powerful than I thought). How can I uninstall Lubuntu and reinstall Windows 8, then Install Xubuntu?

Important information:

• No recovery disk, so I have to use the built-in option


• No CD drive, so I have to use a USB


• I know how to install Xubuntu, so I really need to know how to get rid of Lubuntu and reinstall Windows 8

Thanks for your help.