As time goes by, your computer’s performance can start to suffer as lots of different programs and websites fill up its working areas, and every so often they need a good clear-out.
It is just like servicing a car, and as such there can be quite a bit to remember.
All operating systems work best when at least 20% of the drive is kept free. You can make room by deleting unwanted photos, music and documents or by archiving your data on to removable storage like writable CDs.
Alternatively, with the cost of hard drives falling all the time, try buying a second drive to store your documents separately to the operating system.