Delete sites and site collections
A site administrator who has a Full Control permission level can delete a specific subsite in the site collection or the entire site collection.
On the home page of the portal site, click the Site Actions menu, rest the pointer on Site Settings, and then click Modify All Site Settings.
On the Site Settings page, in the Site Administration section, click Sites and workspaces.
Next to the name of the site that you want to delete, click Delete, and then click Delete again on the confirmation page.
When you delete a top-level Web site, you also delete any subsites beneath it. Before you delete a site, be sure to verify that there are no subsites beneath it, or that you no longer need the subsites beneath it. You cannot recover a subsite unless you have a backup version of it.