One of Defender's more useful features is its Software Explorer, which provides help beyond spyware. Software Explorer lets you see programs running on your PC in a variety of categories, including Startup Programs and Currently Running Programs. It provides in-depth information about each program, including its name, executable file, publisher, path, file size, and other information. You can enable, disable or remove any program.

Windows Defender doesn't give a whole lot of advice in helping you decide which programs you should let run -- but on the other hand, if Windows Defender allows a program to run, it considers the program safe. You can always do a Google search to track down any application about which you're suspicious, and Windows Defender gives you plenty of information about each app, so it should be easy to do a search.

What, no anti-virus?

As with past versions of Windows, Windows Vista doesn't include any anti-virus software. Why? One reason might be anti-trust concerns, particularly in Europe. Including anti-virus in the operating system could certainly be construed as anti-competitive, and could embroil Microsoft in lawsuits for years to come. In fact, Microsoft has been wrangling with security vendors who want access Security Center so that they can more easily integrate into it. We won't go into all the gory details, but the food fight will be with us for some time.

Another potential reason is that Microsoft just happens to sell an anti-virus product of its own bundled into Windows Live OneCare. If anti-virus was included in Windows Vista, there'd be little reason for anyone to buy OneCare.