Which "backup files" are you referring to? Do you mean restore points, duplicate files created by a third-party backup utility, or something else? Windows itself has several groups of files that could fall into that category and other softwares even more, so let us know. Also, be sure to include which operating system you are running...it can chance from OS to OS.
As to defragging, it actually shouldn't have any noticeable effect on the amount of free space available. How much are you 'losing' each time, and out of how much?
Let us know.
John
Where are all the backup files stored when defragging, updating software, etc. and can any or some of thee files be safely deleted? Each time I defrag, I lose disk space.

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