Helping people with computers... one answer at a time.
When you run Windows a large number of processes run. Some are optional, some not. Unfortunately there's no clear way to tell which should be which.
Can you please tell me what programs I should have running in the background as my PC has slowed down, especially when opening applications. I am running Win XP SP2 Home.
No, I can't.
It's not that I don't want to, honest. If I could provide a comprehensive list of what you do and don't need, I would.
The problem is that it's nowhere near that simple.
The fundamental problem is that everyone's list is different. What should be running on your machine is not the same as what should be running on someone else's machine.
Why is it so different for everyone? Because people's machines are different, and how people use their machines is different.
And, of course, what people care about is different.
Hardware differences can manifest as different helper applications running on the machine. Your video card, for example, might include an important utility to manage your video settings. Removing that utility might cause the video card to be unable to do everything you might want. And that's just an example, almost every peripheral on your machine could have something similar. Note that I'm not saying that it does, I'm simply saying that different manufacturers of different peripherals could choose to provide additional software that runs and shows up in your list of running programs.
Configuration differences in Windows itself will frequently manifest as differences in the processes showing up in your task list.
Installed software will often install helper applications that run all the time and show up in the task list. Naturally not all people install the same software, so that list will be different from person to person. As just one example, consider all the different anti-spyware and anti-virus software that's out there - depending on which you choose to run, each will have a different impact on the running process list on your machine.
How you use your computer can have a big impact. Perhaps you run programs and leave them running; perhaps you run programs that, as part of their operation, run other programs that you might not know about or recognize.
Personal preference is a theme across much of the above. For example, perhaps you like the QuickTime icon on your tray; that's one difference right there between your machine and mine. What you want is almost as big a part in all this as what you need.
Software complexity makes this even harder. I'm thinking here of the infamous "SVCHOST" process that in actuality hosts other processes; often several at a time. You'll see several svchost.exe processes running at all times, and that's normal. And turning off some system services may, or may not, impact what you see.
That's a really long list of excuses for why I can't give you a simple list of what you need and what you don't. That list doesn't exist; our machines are simply too different and customizable.
Now, having said all that, you can do some research and make some decisions about some of what you're finding on your machine.
Let me start by throwing out my usual mantra: backup. If you're about to make configuration changes to your machine, potentially turning off software and services that you could find out after the fact were required, you're going to want a full system backup to go back to. It's the fastest, and the safest way to protect yourself.
I have these suggestions:
Use Process Explorer to examine the running processes on your machine. It'll often show the descriptive text that's included with many executables, and that might be enough to answer the age-old "what's this?" question.
Use Google for the processes you don't recognize. Nine times out of ten the answer is there in one of the first results. Many sites, even though they might be selling a product, also include good, basic information as well. A good example is liutilities, or Uniblue; they're a frequent result when searching for a specific ".exe" or ".dll", and while they try hard to sell you their product, the basic information they provide for free on the search results page can often be enough to answer your question. Wikipedia can also be a good resource for very basic information. And of course you'll also find a few right here on Ask Leo!.
Use Black Viper's list of services to evaluate which system services you need to have running on your machine. Lists are provided for both Windows XP and now Vista. It's a little techie, and as I said, you'll have to make decisions based on your understanding of your own needs, but Black Viper provides a ton of valuable information.
By the way, all that assumed you have a properly working and clean machine. If you have spyware, viruses or a rootkit on your machine, things get significantly more difficult. Step one would be to ensure that your machine is virus and spyware free.