Number 10 on "Top 10 Most Useful Free Programs" is SpyBot Search and Destroy (available at www.safer-networking.org).
As many of you know your pcs usually become slower over time. This is usually due to spamware, spyware or viruses. SpyBot is one of my favorite removal programs due to its ease of use as well as the available advanced features.
The main screen (see below image) is very simple. You really just need to click the update icon to check for program updates (the free version does not do this automatically) then click the "Check for problems" button.
The scan will take anywhere from 10 mins to 3 hours or longer depending on how much data is on your computer.
The advanced features are enabled from the Mode Menu Option (just select Advanced Mode)
On the addtional screens that become available are some very helpful options to remove various types of infections. There is a system startup page that detail what is being run when your pc starts. You have the option to disable the item or delete it entirely.
Another nice feature about Spybot is that is give you an option to "Immunize" your system. The theory is to help prevent any future infections of older spam/spware definition.
i would also like to mention that even though this is a free program it included an app called "Tea Timer" that runs in your task tray and watches in real time for changes to various startup location so if a program is attempting to install without your knowledge you will be notified. When a change is detected you will be given the option to allow or deny the change.
I can count the number of client PCs that this program has help me clean. I consider this one to be a must in your pc cleaners tool kit.