CCleaner is a free utility that can be downloaded from Piriform here: http://www.piriform.com/ccleaner
CCleaner's main feature is its "cleaner" functionality: For the most part, it just finds junk or duplicate files and terminates them in classic T-800 style. Searching through cookies, internet temp files, run cache, recent document tmps, explorer MRUs, thumbnail cache, the clipboard, recycling bin junk, and old log files can result in -- at times -- gigabytes of freed up data. The analyze button checks to see how much there is to actually obliterate, which can be followed up by a quick click of the "Run Cleaner" button to remove all those unwanted files. Simple.
The registry cleaner offers another simple-yet-effective blaster feature. CCleaner scans the host computer's registry for errors, duplicate content, broken content, and orphaned content (remnants from uninstalled applications) and then gives the option to fix the errors it finds. It also, smartly so, prompts the user to save a backup prior to fixes in the event that more problems spring up.
The Tools tab has rapidly become one of my favorites: The CCleaner uninstall option attempts to cleanly remove unwanted programs (hopefully destroying residual registry entries or other hidden files), optimize startup applications, manage system restores, and perform a drive-wide file shredding process (since your deleted files aren't actually deleted).
The Uninstall tab not only uninstalls programs, but also allows for entry deletion and renaming, searching, and exporting to text files. The Startup menu, quite simply, is a fancier version of msconfig -- you can select what programs you'd like to run when your system starts up, delete programs from the list, and export your current list to a text file (in the event you want to revert later). Be careful when deleting things, though -- always ask in the comments section below if you're unsure of what is required for Windows.
System Restore has been a powerful tool over the years (despite its early life as the 'virus incubator'), but accumulating restore points can be a massive waste of space. Be sure to retain a "known good" restore and a few other recent points, but get rid of any you don't need (or suspect are infected) by using CCleaner. All of your restore points are listed here and you can restore your computer from here, again bypassing the control panel.
The last feature of the Tools tab is the drive wiper. Here you can securely perform multiple overwrite passes on any "deleted" content from your drives, hopefully obliterating it for good. Perform 35 shredder passes for the most thorough security. You can also format the entire drive, but there's not much special about that.
Always run several drive wiping tools before selling an old hard drive.
CCleaner's Options panel gives access to several powerful configuration options, allowing you to set CCleaner up to your tastes. Selecting cookies worth saving, folders to ignore, folders to focus on, and startup options will personalize CCleaner to your uses.
We try to cover as many of these invaluable software packages as possible, so if you have any suggestions, questions, or comments - please leave them below!
Now for those waffles in version 4.0...
-Michael "Mik" Mann.