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what happens to your computer when you compress your old files when running disk clean up

Anonymous
2012-01-29T17:52:51+00:00

do you lose any important info as a result  of choosing this option?

Windows for home | Previous Windows versions | Performance and system failures

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  1. LemP 74,930 Reputation points Volunteer Moderator
    2012-01-29T18:58:38+00:00

    No, you don't lose anything.  As the option says, "old" files are compressed, not deleted.  The compression algorithm is "lossless" and no information is lost. 

    IIRC, the default for "old" is "hasn't been touched in 7 days," but whatever the period is, it can be changed by clicking the "Options" button in the Disk Cleanup Utility.

    Many peopledisable this function of the Disk Cleanup Utility because it can take a long time to scan all the files and determine which files are eligible to be compressed.  Back when hard drives were small, it was perhaps useful to trade a slight increase in file access time for more hard drive space.  These days, it doesn't seem worthwhile.

    If you do select "compress old files" -- and if you haven't changed your default settings in Windows Explorer -- you will notice that some file names are shown in blue; those are the compressed files.

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  2. Anonymous
    2012-01-29T19:56:23+00:00

    Double what LemP says and:

    The worst that could happen is you compress your NTLDR file and then your system will no longer boot ;) and you will see this familiar message:

    NTLDR is compressed.  Press CRTL-ALT-DEL to restart.

    Then I would be compelled to ask  "Did you run Disk Cleanup?"  Yes.

    I have never seen a way to adjust what XP considers to be a file that might need compressing - if LemP could tell me where that is I would sure like to know.  I have never gotten and answer to that question and I have files that are 9 years old and never get compressed.  I just gave up on trying to understand it.

    I recommend disabling it as Disk Cleanup will hang or appear to hang if you have a million+ files on your system for it to look through.  MS must know about this undocumented feature since they have a KB article that tells you how to do it!

    And, let's say you end up compressing a bunch if files and then need them.  Then XP will have to uncompress them before they can be used and that will slow you down.  Compression was cool when HDD space was tight, but nowadays I just don't get it.

    DC will be zooming after you disable that feature!

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