control panel ->user accounts and family safety->credential manager
you can delete any stored web credentials
You don't have to log into a Microsoft account on windows 8 (except if you want to run Some metro apps or buy from the Microsoft store). If you are only use the desktop you can log into a local account that is validated by your machine.
you can just log on to a local account (make one via control panel)
or you can go to PC settings->users then for your account
select "switch to a local account" option.
I keep two accounts, a local admin account and the Microsoft account. I generally just log on with my local account and use the desktop. I don't switch my Microsoft account to local because someday I might need to access the metro apps and don't want to have to set up the accounts, pin number, trust relationships and such again.