First thing's first - Task Manager

So what do you do when you've been infected? I'm just going to be generic here, a lot of viruses tend to have very similiar behaviour anyway.

First thing's first, try the obvious options. Open the Task Manager integrated into Windows by pressing Ctrl, Alt and Delete at the same time. Depending on your version of Windows, and the way it has been set up, one of two things will pop up.  You may get a full screen interface, with the option to select "Start Task Manager", or the Task Manager might just pop up straight away.  Now that you're in the Task Manager, the default tab is the "Applications" tab. Basically this just lists everything you see in the taskbar, and gives you the option to switch to that application, close it off, or start a new one entirely.

The second tab is the "Processes" tab. This one is similiar, but show's alot more detail, and also show's the programs running that you can't see. It is very handy when it comes to locating malicious programs, or even just finding the cause of a slow computer because of an application hogging the resources.  The easiest way to use this is by clicking one of the buttons at the top of the program list ("Image Name, User Name, CPU, etc"). This will arrange the programs alphabetically by which ever button was clicked.  Usually, a malicious program will stick right out in this list, especially if you are familiar with what you should have running in the background.  Viruses will also often have very dodgy looking filenames, like something along the lines of "kfdhsufnw.exe", for example.

The CPU arrangement option is great for finding a cause of a slow computer too. Often you can find a program not responding in the background, eating all of the computers resources while it's at it. It works by arranging programs in a percentage styled list. 00 meaning the application is using next to nothing in CPU resources, and 99 meaning its chewing through all of it (which would indeed make it very slow).

If you encounter any of the above symptoms / problems, the End Process button can be a quick fix.  It will stop the program from running completely, and close it off.  Be sure not to do it if you have any unsaved progress in the program you're about to end however, it will be lost!  To use it, simply highlight the program in the process list and click on the End Process button, or alternatively, you can just highlight the program and press the Delete key.  Keep in mind, this does not delete the program, it just stops it from running. You can execute it again if need be.  It is also not a permanant fix for viruses, they will often come back either straight away, or next time the computer starts.