Though I might be thinking Hijack This Sucker! or Hijack This @%!$! when I fire up this super-handy system snooper, I suppose the simple HijackThis moniker the original authors applied has just the right amount of attitude. Recently acquired by Trend Micro of anti-virus fame, this sniffer/cleanup utility searches autorun items, processes, services, and the Windows registry for the kinds of entries and activities that hackers use to invade and infect your system.
HijackThis 2.0.2 is a great malware removal tool, but it's not for the average user. The list it generates is full of innocent or harmless entries and items that should be there. Its main intent is to show you what's what, not make a determination of what's actually a threat--so utilizing it effectively requires a fair amount of knowledge. You can select items on the list and have the program delete them, so if you don't know what you're doing, you can create quite a mess despite the automatic backup function that allows you to restore items you've removed. HijackThis's other features include a handy process viewer and an ignore list that you can place items you've deemed as innocent to so they're not scanned in the future.
Even if you don't use HijackThis to actually remove threatening items, it's handy for learning about what they are and can be used for. Simply select an entry on the list and click on the "Info on selected Item..." button for information on what the item is and an example of how it might be used malevolently. Just stay away from the "Fix checked" button until you're confident that you know what you're about to zap.
--Jon L. Jacobi