Lavasofts Ad-Aware (Free Version) is a good companion to Spybot Search and Destory.

now the Defrag that is included with Windows is a Lite version of former Executive Softwares Defrag suite.  Now Diskeeper.  http://www.diskeeper.com/defrag.asp

What I like about the full version, is that it allows you to defrag you're hard drive on Boot-Up.  So what that means is, everything is defraged on you're drive before windows has loaded.  Once windows is loaded some files are locked and cannot be defraged, which is where other defrag programs including the lite version included with windows fails.