With a little thought one can come up with reasons why periodically purging unwanted files, especially large ones, can help with your system performance. How fast your PC operates during file accesses can be a function of the total file count stored there. The reason for this behaviour is that the FAT tables grow in size and the HDD works harder as files are requested by the user. And as a result of saving files and deleting them, files are no longer contiguous and this reduces the rate at which file data can be retrieved from disk. Data security is also a factor, the more files you have that you would rather keep secret, there is increased risk that someone else using the computer might discover them. Cleaning these up can give us back space which is better for obvious reasons.

An enormous range of cleaning tools exist that can approach 'cleaning out a hard disk' from different angles. One common class of application is the illegal porn detection type, and many can be found on the internet. Also remember that there is much more that these software tools can do, for example some can perform drive 'washing', check the drive for porn and remove it, discover and clean copyrighted material, and reveal where all the free space on your disk has gone.