In order to keep your computer running smoothly it needs some free space

If your computer is two or three years old or you’ve got a
lot of files stored on it, it’s possible that the hard drive
could be filling up.

Windows uses the hard drive to store things temporarily
sometimes, and you need to make sure you have some space
left on the drive. If your hard drive fills up to the point
that there isn’t enough space for Windows to work, your
computer can slow down to a crawl.

It’s a good idea to always make sure you have at least 100MB
of free space, if not more. You can check this by
right-clicking on the C: drive icon in My Computer and then
left-clicking on Properties in the menu that pops up.

The properties window will tell you how much free space is
left on the drive. Make sure it has at least 100MB (100,000
bytes) available. If it has less than that, it might be time
to do a little housecleaning and delete anything that is
just taking up space but you don’t need.