Themes have 'glitches' on my site

Almost all the themes I've installed don't look like the screenshot. Fun theme's third column contains: 'Search the site', 'Member Profile', 'Random Blogs'. Where did they come from and how can I control them. They don't show up in widgets so I can't control them. Also, there's a blank column space before the third column and can't get to Dashboard from My Blogs unless I click on My Blogs and then Dashboard, New Post, Manage Posts, etc. will show up. Community theme looks even worse. I don't know, maybe I should start from scratch. Please help.