Of all the tips and tricks suggested to increase the speed of your computer very few, will have any noticeable effect. The main reason your computer is running slow is because of the amount of work it is doing. This can be improved in a number of ways: the easiest being to increase the amount of RAM (Random Access Memory). This is how it's done:

1. Turn on your PC,
2. Start (if XP) / Right-click My Computer / Choose properties. In the dialogue box that appears, choose the General tab, in which you will see details of the System. Among which, you will see the amount of RAM (typically 512 MB)

3. Shut down your computer.
4. Turn off the power at the mains but do not unplug it (So you have earth [ground] continuity).
5. Unplug the keyboard, the mouse, the monitor, and any other peripherals.
6. Remove the side of the computer.
*Be careful not to touch any electronic parts at this stage and if you have an anti-static cable attach it to yourself and to the case of the computer.
Check the memory. It is important that it is the same type as the original. It is best to remove it and take it to your local computer shop.
7. Remove memory by releasing the clips at either end of the memory and carefully pull it out.
Always buy the most you can afford.

Once you have the new memory, replace it in the slot(s) and secure it with the clips.
8. Reconnect all peripherals and turn on the power.
Check that the memory has increased by:
Start (if XP) / Right-click My Computer / Choose properties. In the dialogue box that appears, choose the General tab, in which you will see details of the System. You should now see the amount of memory has increased