"No offense, but I have to disagree that they are still debating whether registry cleaning is a good idea.
Keeping the registry size down by eliminating references to programs that have been uninstalled and are leftover in the registry helps Windows boot faster. This could amount to hundreds of keys and thousands of values, especially under the HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID branch."
As I say, it is still debatable. I don't think you will find a Microsoft reccomendation for cleaning the registry. Pctools may well be different, but most registry cleaners actually do a very superficial task when cleaning. Few would touch the branch you have indicated. I would not deny, however, that if you are in the habit of installing and uninstalling programs, it is beneficial to clean out superfluous program periodically. But the overall result of this task alone, is a small improvement in startup time, if this is a major consideration.
This is what the consumers association has to say, for example.
"The Windows registry is a massive database of almost every setting imaginable for every application on your system. Does it make sense that cleaning it out would improve performance? Sadly it's just a marketing gimmick designed to sell registry cleaner products, as the reality is quite different... registry cleaners only remove a very small number of unused keys, which won't help performance when you consider the hundreds of thousands of keys in the registry.
This isn't to say they are completely useless, of course. Cleaning the registry when you are trying to troubleshoot a problem caused by uninstalling buggy software that leaves entries behind, for example. Even so, most cleaners leave behind the main entries in the "software" sections of the registry. To go a step further: DonÃ¢â‚¬â„¢t run registry cleaner programs, period. We wonÃ¢â‚¬â„¢t go so far as to call them snake oil, but what possible performance benefits can you get from Ã¢â‚¬Å“cleaning upÃ¢â‚¬Â unneeded registry entries and eliminating a few stray DLL files? good registry cleaners, by the way, do not delete .dat files and other system designated handles."
As I said, In spite of the several advices such as this, I will go on cleaning my own!!
By the way, have you noticed that, after a clean install and your own brief personal customisation, how many reg entries are marked for deletion? I filed this, tongue nin cheeck, as feedback with Vista and, subsequently with Windows 7, but got no answer other than the usal acknowledgement