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I am now managing Windows Server 2003 originally setup by someone else.

What I noticed is that even though file compression is not turned on at the drive level (when I go to drive Properties "Compress drive to save disk space" is unchecked) a lot of files are still compressed on the disk seemingly at random. For example in "C:\Windows" folder about half of the files are compressed (appear blue in Windows Explorer and have "AC" attributes) and another half is not compressed.

What I want to do is to disable compression because we have more then enough disc space and compression just slows things down.

Is there some other option (other than disc properties) where file compression is controlled? Can this attribute be changed by some process? I just don't think someone went through thousands of files on the disc and hand-picked them for compression.

Whatever the reason - how would I go about disabling it completely? Using ATTRIB.EXE on the drive root folder recursively?

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OK, I figured it out it seems. Compressing files seems to be the part of Windows "Disc Cleanup" process. More details here:… – Joe Schmoe May 25 '12 at 15:07
up vote 3 down vote accepted

Now that you've figured out why they're compressed, you can uncompress them by running the following from a command prompt on the root drive:

compact /u /s

In addition, when running the Disk Cleanup utility, the option to compress old files is just that, an option. If you don't want to compress old files as part of the cleanup then unselect the check box.

This is the correct command line for uncompressing the entire C drive:

compact /u /s:C:\ /i *.*

Run that from the command line and wait....

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Better usage is this: "compact /u /s /i" - this will ignore errors accessing files that are now locked by the OS – Joe Schmoe May 25 '12 at 19:09

use the command line tool, compact to remove it from directories. however unlike the above use it correctly:

compact /u /s:Windows /i .

that will uncompress all files under the windows folder

compact /u /s:C:\ /i .

that will uncompress all files under the C: drive

your welcome!

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