Windows is obviously a multi-tasking environment and its able to do this by splitting processing time  between multiple applications and background processes very rapidly via threads in order to create a steady seamless stream of processing for the numerous background processes and applications. Generally when using a host instance of an OS on a local system it generally doesn't present too much of a problem when leaving it in its default state without any alteration if you have enough local system resources and processing power to handle it. However there might be times when your system begins to throw fits off the back a particular newly installed app that comes with additional always running background processes where it hadn't done before. This is especially worrying if you've recently installed a new app and you've not even actually got the app started for actual use for it to cause your system to be sweating over a 90 to 100% threshold of processor usage whilst in idle mode. Then when actually launching your newly installed app it will cause your system to constantly run at 100% flat out. At this point you've got a number of options. 

- Buy more RAM and/or a faster processor . Usually increasing the amount of system RAM will resolve this in most cases. However if you have plenty (which is roughly 3 to 4GB for most applications) and its still happening you might want to consider upgrading the processor too.  If it is the case that your system should be able to handle your newly installed app in its current state and a hardware upgrade is a little beyond your budget at the current moment in time you have a number of other option.

- Uninstall the application and don't use it again. However this does kind of defeat the object of having your computer in the first place if it is the case that you know your system is capable or at least should be capable of handling the said newly installed application. So alternately you might want to consider checking to see what processes are running and fine tuning the settings for these.

The Task manager

From here you'll be able to see all application and background processes that are currently running on your system and consequently what your processor is actually giving its time over to. 

I'm pretty much a stickler for minimizing the amount of unnecessary junk on my system so I'm forever dropping into the Task Manager at the slightest hint of anything causing something that resembles a speed bump. Not to mention I'd also gone to the trouble of doing a fresh OS install to then try to keep off apps that I know aren't essential  to making my host OS work or could potentially come with a significant performance overhead with it.  In many cases you'll find that without the actual app even being launched there'll be additional background processes that come with it that constantly run post installation. Sure I could always install stuff and then uninstall it again later but even this leaves junk behind on your system, causes the usage of additional drive space even after you've uninstalled stuff (for restore and roll back purposes), and potentially creates registry dependencies that weren't there prior to installing particular apps even after removal which the system still reads and actions even if it contains loop back conditionals and takes a longer route then it would normally just to perform the same task. It also has the effect of leaving redundant registry entries that your system still takes time to read every single time it boots up too.    

For others that aren't quite this anally retentive about such things you'll often find it’s the case there will be a lot of background processes and applications running that aren't even essential to the running of your system as far as your need to do things on your personal computer goes. This will obviously be using up processor time slots and system memory unnecessarily. This is especially so the case if you bought a system with a pre-installed OEM OS with a bunch OEM software. Its often the case that manufacturers will include a lot of "bloat ware" along with it. This is just my personal opinion but this might also include the actual bundled premium anti-virus checker. Why? Well to all intents and purposes a well known premium real time virus checkers will do as stated, i.e. Protect your computer and stop unwanted stuff getting onto your system. However I've never actually encountered a light weight third party premium anti-virus program (or a none third party premium real time anti-virus program for that matter) in my life. Its generally the case in all my years of testing these things that most well known premium virus checkers cause noticeable system slow down in comparison to how it ran just prior to installing it. Or if it’s the case that it was included with a system, the removal of it will in fact cause a system to noticeably run significantly faster. I guess in more recent years programs such as Norton has got a damn sight better for this issue since there doesn't appear to be any slow down when using the most recent iteration of it on a plugged in desktop system with sufficient hardware resources or laptop whilst having the mains power supply available.  However when using a laptop on battery mode you will notice the difference especially when switching to "power save" settings, that is to say a laptop will run much faster without the premium real time virus checker installed when running on batteries. Although the actual figures might look very similar on the percentage readout front you will notice the actual difference in terms of actual system speed with some of the premium options. Also if its idling at 20% or higher its definitely too much as Essentials will idle at 0 to 5% whilst fully in action on an appropriately configured system even in "power save" mode with no decrease in system speed. Or at least it was the case on my particular system in how I had configured it.

There's a very good reason for why I use it other than its free

Microsoft security essentials is free to download and install on your Windows based OS if it is indeed a validated and registered Windows OS. But why would I advocate it so much against the many premium options? Like I said I've tested many of the premium options with full subscriptions. Often it’s the case that there will be promotions where you can get a year to 2 year free subscription on premium anti-virus software anyway. From experience MS security essential for the past 4 to 5 years is a very light weight and fast real time virus scanner that has very little noticeable impact on system performance, that’s even when only running on batteries from a laptop in power save mode. This certainly wasn't the case in its beta test phase and for a year or so in its post release form. There isn't much of a noticeable difference  in performance with or without MS security essentials real time anti-virus checker installed to any of my Windows OS as far as any potential system slow down goes. Prior to that I used to use OneCare on my main system which I have to admit was quite sluggish and also required a premium based subscription. There's also the fact that essentials has a very good if not an excellent high level of detection with regular pattern update releases. If you think about it, since you are using a Microsoft OS there isn't much additional access MS could potentially gain to your system via an official MS created anti-virus checker since they could have potentially already included it in the actual MS Windows OS with little trouble. The main reason I always recommend Security essential is down to the fact that you get premium like real time virus protection and its extremely light weight and fast with barely noticeable performance impact/overhead. 

Also a lot of the premium virus checkers will also include a software based firewall with them. Don't get me wrong, they're usually very good, however if you are running a version of Windows created on the server build used for Vista or windows 7 the built in firewall included will more then adequately already do what these firewalls do with far less processor and system memory overhead/load if configured properly.

But back to unnecessary processes

If you don't actually know what you're looking to kill in the task manager, uninstalling apps from the program manager that you know you don't need or don't actually use might be a starting point. This will help to remove many of the background processes that aren't actually directly useful to how you individually use your computer and what you use it for. Doing this will also permanently remove the unnecessary resource sapping processes often caused by "bloat ware"/premium limited period trial software/bits of software with background processes with reminders trying to sell you stuff you don't want without you having to constantly drop into task manager to prune the active task list at each power cycle and log in. 

There might also be a number of OEM control software included for the various bits of hardware such as the wireless connection which Windows can pretty much fully handle without it and with significantly less use of processing resources and memory. Its more often the case that removing it will further increase system performance and speed. It also closes a number of channels of potentially unwanted access. This also generally allows for Windows built in control feature to manage it for you. However there are a few exceptions where removing this software will render it completely none functional on some laptop systems if its not configured correctly due to some of the default Windows OS components having been altered. 

Remove included default OS components such as Windows media center if you're not actually using it…

I like Windows media center. The problem is that I never actually use it since I have iTunes for organising and listening to my music as well as WMP for quickly streaming video off the net already. MCE is another application that leaves background processes running at every log in after its initial launch. In fact its something that will cause a noticeable hit in system performance even if it has never been launched on your system before whilst still resident as an installed component. If you don't actually use it I'd recommend removing it after which you'll notice a marked increase in speed on your system. There is always the option to re-activate/re-install it later if you should decide you want to use it afterwards for whatever reason.

If you're not gaming on it you don't necessarily need to pump more voltage through it to push a higher current across the silicon chips to speed it up (although it will speed it up within a certain threshold if you do before it actually over heats and slows down your system anyway due to the laws of thermal dynamics)

Doing these things will certainly bring your system a markedly noticeable boost in actual speed as well as significantly reduce the amount of processor overhead which in turn also reduces electrical power consumption required for the same computing tasks. However for none gaming use there are a few more things that can be done to reduce processor overhead/load and increase system speed even further without having to upgrade hardware or over clock it if it is indeed within the bounds of required hardware specification for your chosen application which I'll cover in "Managing process priority".