HELP! My computer is getting slow!

Does this sound familiar to you? You may be thinking "I need a new computer."  STOP!  You most likely do NOT need a new computer -- you just need to do a bit of Spring Cleaning, so to speak...
It is an established fact that computers collect all kinds of unwanted stuff over time, which has the combined effect of slowing your once-quick computer to a crawl... But how can I get rid of all that stuff? Thankfully it is really pretty easy:

1. Clean up your hard drive.   Windows has a nice little utility to help you get rid of all of those old unnecessary files that are taking up extra space on your hard drive. To find it, open your start menu, and point to "All Programs" then "Accessories", then in "System Tools" click on "Disk Cleanup".  Alternately, you can just type "cleanmgr" into the search/run box and hit "Enter"   The computer may then prompt you to confirm which disk you want to clean up, (If you have multiple hard drives) simply click "Ok" to continue... The computer will then prompt you to confirm what you want to delete, (it is safe to select any or all of the check boxes, it will not delete any of your personal files.) And click "Ok" to finish. You're done!
2. Defragment your hard drive. When your computer saves a file to the hard drive, it pretty much just plunks it down in the most convenient place... Imagine if you were to throw all of your clothes into one dresser drawer, without any kind of folding or sorting whatsoever. While it is true that all of your clothes would be in your dresser, it would probably take a long time to find a pair of socks... This is the same problem your computer has: while all of the files are there, they are all just thrown together in some random way, and the computer takes a long time to find the pair of socks it is looking for... Thus the process called Defragmentation, where your computer simply rearranges all of the files into a nice little stack. :-)  IMPORTANT NOTE: Windows Vista and Windows 7 automatically run the defragmentor on a schedule, so if you are running either of those Operating Systems, rest easy, your computer is a step ahead of you! :-)  For those of you who are running XP or earlier, you will find the disk defragmentor in the same directory as "Disk Cleanup" in section one above...
3. Clean up your computer's Registry.   The computer's registry is much like an inventory sheet, it is where the computer looks when it wants to know where to find something. The registry keeps an active list of all of the installed programs, as well as many settings and a whole lot of other information.  The problem is that over time the registry ends up collecting a lot of unneeded information, which does nobody any good, and only serves to confuse the computer... Unfortunately, Windows still doesn't come with a registry cleaner, so for this step you will need a good 3rd party software: I use CCleaner from Piriform.  If you need help using CCleaner, check out this quick tutorial.
4. Use a good Anti-Virus program.  This is an important step in protecting your computer from malicious software, viruses and malware.  Although there are many good programs out on the market these days, most of them require you to purchase some software or a subscription to the service. Seeing as I am a notorious cheapskate, my favorite program is AVG AntiVirus Free. Yup, absolutely FREE!  I can unreservedly endorse their software, as I have been using it for severely years now on multiple computers with absolutely NO problems! You can pick up a copy here: AVG AntiVirus FREE    NOTE: The above four suggestions are mostly pretty easy, and can be done by anybody. The remaining suggestions are a little more risky, and should only be attempted by those who are familiar with their computers, and who know what I am talking about... CONTINUE AT YOUR OWN RISK!
5. Uninstall un-needed, un-necessary, and un-used programs.  If you know you are never going to use a program again, you can uninstall it and regain the wasted hard drive space, and often also free up computer resources. To uninstall a program, open your start menu, then click "Control Panel". Once in the control panel, click on "Add or Remove Programs" (Windows XP) or "Uninstall a program" (Windows Vista/7)  This will bring up a list of installed programs on your computer, which you can go through, and then decide if you want to get rid of any of them...
6. Disable startup tasks/services.   WARNING! Disabling system services may cause your computer to become irresponsive, to act strangely, or otherwise cause undesirable results. THIS IS NOT FOR BEGINNERS! PROCEED AT YOUR OWN RISK!    This is an advanced process, although one which is completely reversible.    If you are really wanting to increase your startup time, or to decrease the amount of active threads, you can disable some unnecessary startup tasks... You can access the System Configuration window by typing "msconfig" into the run/search box and hit "Enter".  From the following window, you can enable or disable startup programs and services under the respective tabs... For more information on this subject you may want to check out the following site: Computer Tips Free

Well, I hope that helps you all to get your computers running faster, and more productively.  If you have any questions, feel free to leave them in the comments, and I will do my best to answer them.
    Andrew B.