1. Empty Your Recycle Bin
Locate the little garbage can on your computer screen desktop. Place the mouse pointer on the garbage can icon, and click the right button on the mouse. That should open a small menu that will give you the open to Empty Recycle Bin.

2. Clean Up Hard Disk
Your computer stores lots of temporary files and back up files over time. Even while surfing the internet, your computer will store a lot of information that you don't need. There is a function available called Disk Clean Up.If it asks you which hard drive, select drive C: as that is your main drive most likely.

Go to Start Button> Programs> Accessories > Disk Clean Up

This process call take awhile to analyze the hard drive. Once it is done analyzing how much space you can save, it will ask you to confirm that it can delete those files. Select yes and let the process run for awhile. When that is complete, you should move on to the next step.

3. Disk Defragment
Once files are deleted, like in the process above, there is empty space left where it was once saved. When you defragment your disk, it basically pushes all your data together and takes out the empty spaces. This actually allows your computer to access that information faster, as it doesn't have to skim over all that empty space. This process can take a very very long time and I recommend you start it right before you go to bed.

Go to Start Button> Programs> Accessories > Disk Defragmenter

4. Windows Updates
As long as you have a certified copy of Windows XP installed on your computer, you should set your computer up to receive Windows Updates automatically. Once downloaded, there is usually a little exclamation icon by the clock. This little yellow shield with the exclamation mark means you need to install the windows updates that have been downloaded. This can usually be done just by clicking on the yellow shield. To check your settings go to Control Panel > Automatic Updates.