Why have the colours of files changed in Windows Explorer?

Q My PC runs Windows XP with Service Pack 3. Recently some of the files and folders listed in My Documents have changed colour. A similar thing has also started in the My Pictures folder.

The only thing I did around about the time this started was to delete some old compressed files using Scandisk. I have performed a full virus scan but nothing has been detected. Do you have any suggestions, please?
Raymond Glaister

A Windows can display files and folders in different colours when the contents have been either encrypted or compressed. Encrypted files are displayed in green, while files compressed by Windows are displayed in blue.

How did this happen? Well, although you say you used the Scandisk tool we think you might mean Windows XP's Disk Cleanup tool. Scandisk has no part in deleting old or compressed files.

Disk Cleanup, on the other hand, does offer the option to compress old files to save space, but under a heading labelled ‘Files to delete' – hence the confusion. The coloured folders you're seeing are the ones that are now compressed.

Practically, this compression makes no difference whatsoever to the PC's usability: the targeted files and folders will remain accessible but will appear blue when viewed in Windows Explorer. The difference is that they take up a bit less space on your computer's hard disk.

Also, in theory at least, the PC has to put in a little more computing power whenever you work with them, because it has to decompress them first (though in reality, you are unlikely to notice any difference in performance).

If you want to manage how Disk Cleanup determines ‘old' files, first launch the tool as usual (Start menu, then My Computer, right-click on the hard disk, choose Properties then click the Disk Cleanup button).

When the aforementioned Files to delete list appears, scroll down to find the Compress old files entry: click to highlight it then click the Options button below. The ‘Compress after' number specifies how many days a file must be left untouched before Disk Cleanup will apply compression – change it if you want and click OK.

Finally, if you find the colouring of compressed files and folders distracting, the feature can be easily disabled. Launch Windows Explorer, open the Tools menu and choose Folder Options. Select the View tab and scroll down the Advanced settings list to find the entry labelled ‘Show encrypted or compressed NTFS files in color': click to remove the tick and click OK.