I am new at this. My computer has recently started to become slow/sluggish while searching the internet and playing videos. I defrag and disk clean very frequently as well as scan my virus program. I am wondering if it is because I have too many programs running in the background. How do I know which programs I need and which ones to stop and how do I stop those programs from running?
Thanx!!!!

What's your Operating System (XP Home, XP Pro, etc., ....)?
How much RAM do you have (right click My Computer / select Properties / under the General tab, how many MB of RAM do you have)?
What's the size of your harddrive?
How much free space do you have on your harddrive (double click My Computer / right click C: drive / select Properties / under the General tab, Free Space)?

Open the Task Manager (Ctrl+Alt+Del), and click on the Processes tab.
This will show you everything that's running.
Use the Windows Startup Programs Database to check each entry.
It will tell you whether the program is needed, or it can be disabled.
If you have any questions about one, just post back here, with the program in question.

Try to disable the unnecessary programs from inside the program itself, using the Options menu.

To control Startup applications, that can't be disabled from the programs Option menu, use a third-party startup monitor.
Two good ones, are mike Lin's Startup Control Panel, and Startup Inspector.

Always research an entry before stopping it. Stopping the wrong entry could cripple a necessary program, causing problems.

You can also download and use Process Explorer to investigate all running processes and gather additional information to identify and resolve problems.

When you say you Defragment often and scan for viruses, is that all you do? Do you scan for spyware, delete unwanted files or programs, use disk cleanup etc? If you don't then that is probably why it is slow, however forgive me if you do these, it's just because you didn't mention them, hope this helps!

just downloaded the startup inspector. Everything on my start up is unknown to it. Not one item was required or user choice. I find this odd