Hi there!  Here I'll tell you how to clean up and speed up your Windows computer.

Cleaning up your computer involves deleting things from the hard drive that you don't need or use.  Speeding up your computer involves closing/exiting the sneaky programs that are running in the background, even while you're not using them.  We'll start with cleanup.

CleanUp (removing things from the hard drive)

First, click the Start Menu, then Settings, then Control Panel, and choose "Add/Remove Programs".  Once there, remove any programs in the list that you don't need or don't use.  This will delete them from your hard drive, which gives you more space.

Second, right-click on the Start Menu and choose "Open".  [If you don't have that option when you right-click the Start Menu, then go to My Computer, then your C: drive, then the Windows folder, then the Start Menu folder.]  Notice that there's a Programs folder, and if there are any icons on your Start Menu above the Programs folder, they are here too.  Delete any of those icons that you don't use.  This doesn't delete any programs, it just removes those shortcuts, which can also be found under Programs anyway.

Third, look at your desktop.  If you right-click on a blank area (in other words, not on an icon) of the desktop, you'll get a menu with "New" on it, and if you click "New" you'll get the option to make a new folder.  You should make a new folder, and call it "desktop junk", and then move any desktop icons that you don't use into the "desktop junk" folder.  (Good candidates for moving include any files named "New Text Document", "New wav file",  "New folder", etc.)  You can move them just by dragging them with the mouse onto that folder.  Then, if you find that you've moved an icon that you want back, you can just drag it out of that folder and back onto the desktop.  If not, you can delete the "desktop junk" folder after a few days.

Fourth, if you use Internet Explorer (and you should), open it up and click the Tools (or View) menu, then Internet Options.  Once there, look around for the options to Clear History and Delete Temporary Files.  You should do this about once a week to keep things running smoothly.

Last, go to My Computer, then your c: drive, and look for a folder called "Temp" or "Tmp".  Open it up and delete everything in there, unless for some odd reason, you save things there.  Then, go back to your c: drive, then to your Windows folder, and look again for those temp folders, and delete their contents (not the folders themselves).

SpeedUp (removing things from memory, aka RAM)

To speed up your computer is to free up memory (RAM).  You do this by closing or exiting any programs that you're not currently using.  This frees up memory for the programs you are using.  This sounds obvious, but the thing is, there are always programs running in the background that you didn't start and that you don't need to be "always on".  You can think of this like turning off the bedroom light when you're in the kitchen.  You're not "deleting" or removing the light, you're just turning it off until you need it again.  Same with programs on your computer.

Ok.  The easiest place to look is in the system tray, down next to the clock on your taskbar:

That's the taskbar, which is usually at the bottom of your screen if you haven't moved it somewhere else.  The Start Menu (mine's an "A" menu) is on the far left, and the icons next to it are OK.  They aren't running programs, they're just shortcuts to programs.  The longer bars in the middle are your open programs or windows... you should close any of those that you're not currently using.  The small icons on the far right, next to the clock, are in the "system tray", and they are programs that are currently running and taking up memory.  Those are the ones we want to get rid of.

Those icons right next to the clock are all slowing your computer down.  I usually have about 5 icons there.  If you've got about 10 or more then you've got problems.  So first, hold the mouse pointer over the icons, one at a time, to see what each one is.  If it's a program that you're using right now, then it's fine to leave it there.  And some, like Volume Control, are OK -- they take up very little memory.  But most of them you probably don't need to be running.  Remember, by exiting the programs here, you're just closing them until you want to use them again.  You're not deleting anything.  So, right-click on them and look for an "Exit" or "Close" option.  If you can't figure out how to close one, hold the mouse over it to get it's name.  Then press the Ctrl-Alt-Del keys to get the Task Manager, and see if the program is in the list there.  If it is, "End task" on it.

Once you've closed all the ones you're not using, you're on your way.  The only problem is, when you restart your computer, most of them will come back!  To stop that from happening, right-click the Start Menu, choose Open, then Programs, then the Startup folder.  All the items in there start automatically every time your computer starts.  If there's something in there that you don't want to start, then just drag it to your desktop.  You can always put it back if you change your mind, or start it manually by double-clicking the icon you dragged to the desktop.  But, there is an even sneakier place that programs like to automatically start from.  You can find it by clicking Start, Run, then typing msconfig and press enter.  (Windows 98 & ME have msconfig.  If you don't, you can click here to get it.)  Once msconfig starts, click on the Startup tab at the top.  Everything there also automatically starts when your computer starts.  So, uncheck anything you don't want to start (remember, you can always come back and re-check it if you change your mind), and then restart your computer.  If you have any of the following, though, leave them checked -- these are normal Windows processes that are OK:

ScanRegistry
TaskMonitor
SystemTray
LoadPowerProfile (might be there more than once, it's OK)
SchedulingAgent

...but you can uncheck anything else, unless you have some specific reason for leaving it.

Of special note are AOL icons in the system tray, by the clock.  You can always get rid of those.  You don't need that icon down there anytime, not even when you're connected to AOL!  It just sits down there and wastes memory and slows things down.  So get rid of it.

One More Thing...

Now, if you've done all that, your computer is pretty clean and fast.  Two important things to do to keep it that way are scandisk-ing (error-checking) and defragmenting your hard drive.  You can access these by going into My Computer, then right-clicking on your c: drive and choosing Properties.  There you'll find the scandisk and defrag tools.

Each of these two operations can take a couple hours, so it's good to start one before you leave to go somewhere, and just let it run while you're away.  Or, let one run overnight.  You should do these at least once a month to keep your computer running nicely.