Improve your PC's performance by clearing out the clutter
The new year is fast approaching. What better time to give your system a good scrubbing? The best tool I've found for taking out the digital garbage is Piriform's CCleaner. (Quick tip: Click the "Alternative Download" link, not the FileHippo.com link above it. For some reason, the FileHippo page links to a download for a program I never heard of.)
Read this before you install CCleaner! By default, the program wants to add the Yahoo Toolbar to your browser. This lets you run CCleaner from the browser, but I suggest you uncheck that option in the program's installation wizard and instead choose to add a shortcut to CCleaner on your Recycle Bin right-click menu.
There are a couple of things you might want to do before you launch the utility. First, run Windows Update (or Microsoft Update if you use Office or other Microsoft apps). Then open the Add/Remove Programs applet in Control Panel (Vista calls it Programs and Features) and uninstall any apps you no longer use. Updates and uninstalls are the sources of many orphan files and Registry entries that do nothing but take up space on your hard drive and generally get in the way.
Once your system is updated, right-click the Recycle Bin on your desktop or in Windows Explorer and choose Open CCleaner. With the Cleaner option selected in the left pane (it's the default), check the locations you want to clean, or uncheck the folders that the program checks automatically, under both the Windows and Applications tabs. Then click Run Cleaner.
Choose the locations in Windows and your applications that you want CCleaner to scour.
Next, choose the Registry button in the left pane, and click Scan for Issues. When the scan finishes, Select Fix selected issues, and then choose Yes when you're asked if you want to back up changes to the Registry. That way if something goes haywire, you can simply double-click your Registry backup (it's named "cc" plus the date and time) to restore things to their pre-scan state. Once you're back in CCleaner, you can either fix the "issues" one at a time, or all at once by selecting Fix All Selected Issues. Click OK at the warning, and then Close.
CCleaner's Tools option lets you uninstall programs or Startup items, but you don't get any more information about the items listed than you do when you use Windows' own uninstall and startup options.
Technically, CCleaner is donationware, not freeware. If you didn't drop a couple-few dollars in Piriform's Paypal account when you downloaded the program, and you find yourself using it more than once or twice, consider returning to the company's site to make a donation. That's the best way I know of to keep great tools like CCleaner available in the future.
Monday: Use Web tools without sacrificing your privacy.
Dennis O'Reilly has covered PCs and other technologies in print and online since 1985. Along with more than a decade as editor for Ziff-Davis's Computer Select, Dennis edited PC World's award-winning Here's How section for more than seven years. He is a member of the CNET blog Network, and is not an employee of CNET. 
I would like to recommend another free tool called <a href="http://www.pc-kitchen.com">PC-Kitchen's Registry Cleaner</a> that seems to have taken concepts from many different registry cleaner's and organized them into one good user friendly application.