You can change your password under My settings > Accounts. Make sure your password is secure and is at least8 characters long.
It is possible to deactivate your SlideWiki account in My Settings > Account. This will deactivate your log in but all your content will remain public on SlideWiki. To reactivate your account please email firstname.lastname@example.org or use the feedback button. Please make sure you provide the email address you used to log-in.