ickkii makes some valid points. I decided to point out some obvious ways to minimize or eliminate risk on your system, for those that don't want to see the post I put on my website. You need to open your taskmanager and check what services are running on your system. The only windoz I have on a system here is WinXP, which came stock on my netbook. Below is what I do to tweak my system, and I can't stress enough that YOU CAN BREAK THINGS if you try this without reading my previous post on this, especially if you don't know what these services are. Many look benign while allowing remote access to your system files. Not good for your security. Some look hinky while being relatively benign. Read my previous post. For the brave:
The "START" button on the lower-left opens several options. Click "RUN" and type "services.msc" and hit "ENTER". A window will open up showing what services are running on your system. I go down through the list and disable EVERYTHING that allows access/control/sharing of my system from remote locations. There are some of these that your system will not allow you to turn off, so don't worry about those few. Just look at them and read the description of what they are, even though it's brief and/or confusing. Remember what I said about reading my previous post before attempting this? If in doubt, switch it from "AUTOMATIC" to "MANUAL" operation so it only comes on when needed. That way it won't be constantly running and hogging system resources.
When you see how much stuff is running in the background hogging memory/cpu time on your windud system you begin to understand why your machine can bog down over time. I haven't tried much editing of registry files on Vista or Win7/8, which is in use by my dad. A little tweaking that I did do made him feel like he was in turbo mode, though, and I haven't heard much cussing from him about whatever latest malware was trying to infect his system, nor has there been any complaints about how the AV program wouldn't delete the malware because it was "in use by the system"-- a favorite trick of malware writers to prevent you from deleting their work, and a major fault with windoze.
You might want to clear out stuff from your "STARTUP" menu file as well, so you don't have all that hogging system resources. You'll be amazed how much memory and cpu time you freed up just doing this.
The above is a bare-bones minimum intro to what works for me, and I've noticed a couple good PC shops here in town that also use much the same methods. It is meant for those who know their system, but not for those who struggle opening files, programs, installing stuff, or using the mouse. Like I said, I used to wipe my system weekly just for fun back in the Win3x Days, and did the same thing while playing with linux/unix in the early-mid 90's, so I'm not afraid of risk, nor am I lost and gnashing teeth over a garfed system....I simply re-install if needed, which is rarely these days.
Enjoy, and 73