For a long time, storage was relatively expensive so it was a good idea to spend time and money reducing the amount you would needed to use. In 1990, PC hard disks would cost about $0.20 per megabyte, and capacity would be in the 2-3 figure MB range. So, compression software could be used to delay the day you’d need to buy a bigger disk, even if there was a slight impact on performance (through decompressing and re-compressing data while reading from and writing to the disk).

As storage got cheaper, the tendency to just keep old data gained prevalence, though some systems imposed limits due to the relative complexity and expense of managing their data, providing resiliency and backup services.

Corporate email quotas were measured in Megabytes, and tools like the Outlook Thread Compressor helped people reduce the amount of space their mail took up. In time, people used it to simply reduce the number of messages they needed to read, rather than worrying about the space they’d save – and it inspired the Clean Up Folder function in Outlook today.

When Google launched Gmail in 2004 with a staggering mailbox limit of 1GB – 500 times that which was offered by Hotmail – the rules on what was expected for email quotas were re-written, with an expectation that you would never need to delete anything, and could use search to find content within.

Leaving aside corporate policy on data retention, keeping piles of stuff indefinitely causes its own set of problems. How do you know which is the right version? Can you be sure that you have copies of everything you might need, in case the data is lost or damaged? If you have a backup, do you know that it’s a full copy of everything, and not a partial archive? Having multiple copies of the same content can be a headache too, if you’re not sure which is the true original and which might be later copies or partial backups.

Applications might create their own duplicate content – perhaps through bugs, or through user activity. There was a time when syncing content to your phone or to another machine might risk duplication of everything – like having multiple copies of contacts in Outlook, for example. A variety of hacky resource kit utilities were created to help clean up mailboxes of duplicate contacts, appointments etc; you might want to check out a more modern variant if you’re worried that your mailbox is cluttered up.

The curse of duplication can be a problem at home, too, especially when it comes to photographs. Have you ever taken a memory card from a camera, or a backup of an old phone, and copied the whole lot just to be sure you have everything?

Cleaning up the dupes can help make sense of what remains. You could spend money on proper photo archiving and management tools like Adobe Lightroom, or you could roll your own methodology using a mixture of free and low-cost tools – tech pundit Paul Thurrott recently wrote about his approach.

There are many duplicate-removing tools out there – just be sure you’re getting them from a reliable place, free from adware and other nasties. Be wary of anything that purports to “clean” your PC (registry cleaners etc), watch out when accepting T&Cs and don’t allow the setup routine to install any other guff you don’t need. Make sure you have the right protection on your machine, too.

One recommended tool is Duplicate Sweeper – free to try but a princely £15 to buy, but worth the peace of mind that comes with a tidy photo library or Documents folder.