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Windows Registry - Why Clean It?

Before you read the following, if you want to remove a program with all its little pieces in the registry, I would recommend a program called revo unistaller.

An article from Ken Blake, Microsoft MVP

There's no universal answer that's right for everyone under all
circumstances, but two general points about this:

1. As far as "cleaning" is concerned, my view is that most of the
efforts in this regard are completely unneeded and often dangerous. It
depends on what you mean by "cleaning," but most people use the word
to mean getting rid of files (or entries within files) that aren't
needed.
But there are many things you can do in this regard that are
completely safe. For example, you can run Disk Cleanup and do all of
the choices there. No problem and it gets rid of some things you don't
need, thereby saving a little (usually very little) disk space.

Similarly, you can run CCleaner, which does a lot of the same things,
perhaps a little more thoroughly. CCleaner is safe to use, as long
as you don't use its registry cleaning functionality, which is not
safe.

But my view is that many people pay far too much attention to this
sort of thing. Getting rid of unneeded files may be thought of a
cleaning, but typically all it accomplishes is saving a few pennies
worth of disk space. If you are in a situation where those small
amounts of disk space are significant to you, then almost anything you
do will be a stopgap measure and you will quickly find yourself back
in the same situation. Your only real solution is to buy a bigger
drive.

Despite the above paragraph, I don't strenuously to people doing this
as long as they stay far away from most of the third-party software
that you find on the web, telling you how wonderful what it can do for
you is. Most of it is dangerous, and accomplishes nothing really
useful. Stick to Disk Cleanup and CCleaner (again, without its
registry cleaner) and you're safe.

2. Regarding speeding up, the answer depends on what's slowing you
down. There are many possibilities, but I will address the two most
common these days:

a. Malware infection. Many people are greatly under-protected in this
regard. They may run an anti-virus program, but no anti-spyware
programs. And the programs that most people choose are often among the
poorest available (Norton and McAfee, for example, are the most
popular, but in my view, and that of lots of others of us here, they
are among the worst).

For an anti-virus program, I recommend eSet NOD32, if you are willing
to pay for it. If you want a free anti-virus, I recommend one of the
following three:
 
Avira
Avast
Microsoft Security Essentials
 
You also need anti-spyware software. I recommend that you download and
install (both freeware) MalwareBytes AntiMalware and
SuperAntiSpyware.
Two other points regarding malware infection:

1. Be extremely careful what web sites you go to. Some are dangerous,
and just going to one that somebody recommends to you is seldom a wise
thing to do, unless you know it's safe.

2. E-mail attachments can also be sources of malware infection.
Attachments are very risky. You often see advice not to open
attachments from people you don't know. I think that that's one of the
most dangerous pieces of advice you see around, because it implies
that it's safe to do the opposite--open attachments from friends and
relatives. But many viruses spread by sending themselves to everyone
in the infected party's address book, so attachments received from
friends are perhaps the most risky to open.

Even if the attachment legitimately comes from a friend, it can
contain a virus. I'm not suggesting that a friend is likely to send
you a virus on purpose, but if the friend is infected without
realizing it, any attachment he sends you is likely to also be
infected.

I never open attachments at all, except from a very few trusted
sources, and then only when I'm expecting them.
b. Programs starting automatically when you boot, and often running in
the background. Many people not only don't use all the programs they
have running in the background, they often don't even know what they
are.

Here's my standard post on this subject:

First, note that you should be concerned with all programs that
start automatically, not just with those that go into the system tray.
Not all auto-starting programs manifest themselves by an icon in the
tray.

On each program you don't want to start automatically, check its
Options to see if it has the choice not to start (make sure you
actually choose the option not to run it, not just a "don't show icon"
option). Many can easily and best be stopped that way. If that doesn't
work, run MSCONFIG from the Start | Run line, and on the Startup tab,
uncheck the programs you don't want to start automatically.

However, if I were you, I wouldn't do this just for the purpose of
running the minimum number of programs. Despite what many people tell
you, you should be concerned, not with how many of these programs
you run, but which. Some of them can hurt performance severely, but
others have no effect on performance.

Don't just stop programs from running willy-nilly. What you should do
is determine what each program is, what its value is to you, and what
the cost in performance is of its running all the time. You can try
internet searches and ask about specifics here.

Once you have that information, you can make an intelligent informed
decision about what you want to keep and what you want to get rid of.

Ken Blake