Editing your Registry: Why not to do it.
The Windows Registry is an enormous database that maintains the bulk of the configuration settings of your entire PC system. Whether it's a property that has been set in the Control Panel, settings that have been configured by your particular applications, or the various hardware and peripheral operational information, the way that your PC interacts with nearly everything is contained deep within the bowels of the Windows Registry.
Windows' Registry Editor utility is accessed through the run command and then typing in regedit. I'm quite surprised that with its history of bombarding users with all sorts of useless Dialog Boxes in Vista warning "Do you want to do this?" "Do you really want to do this?" and "Do you have confirmation in writing from your psychoanalyst that you are sane enough to know that you really want to do this?" that Microsoft even allows access to regedit by anyone not on Mr. Ballmer's payroll. However, the truth is that you can edit your Registry and in the majority of cases it will be without sufficient knowledge of what you're doing and buy you a non-stop one-way ticket to PC Hell and reformatting/reinstalling your Operating System.
If you are lunatic enough to want to mess around with the sensitive innards of your System, you can open the Registry Editor window which displays the different settings and parameters on the left and the configuration information and values in the right pane. Just double click on any particular subkey in the right pane to display the Edit Value or String window. At this point feel free to enter any new value you want in the Value Data box as you likely will never be able to boot up again so you might as well do as much damage as you can. There is no undo or save command in the Registry Editor so whatever change you make is irreversible unless you manually restore the value to its prior setting and that's really hard to do when your PC is spending its entire day displaying the BIOS Starup screen for two seconds, then blank for ten seconds, then BIOS Starup screen for two seconds, then blank for ten seconds, then...
There are many third party Registry Editing utilities which all have a common theme: They make it easy for you to irrevocably scramble your Registry. The one and only Registry utility I've ever had any success with is CCleaner which is an amazing piece of freeware that I use at least once a day to blow out all the cobwebs that are clogging up my system. CCleaner's Registry Integrity function is not really an editor at all, but a clean up utility which deletes unused and old entries, including File Extensions, ActiveX Controls, ClassIDs, ProgIDs, Uninstallers, Shared DLLs, Fonts, Help Files, Application Paths, Icons, Invalid Shortcuts and does it all by first safely backing up your current Registry settings. In all my years of using CCleaner's automatic Registry functions, I have never ever had to resort to restoring the Registry backup, as it's never once caused a problem. What it has done is to make my system noticeably more responsive and crashproof.
Bottom line: You don't need to edit your Registry, and if you ever did need to, you should just reinstall from fresh, updated, legitimate software. It will save you from countless repair bills and ulcers.