Be careful with VHDs and Windows XP Compressed Folders

Be careful with VHDs and Windows XP Compressed Folders

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Just thought I would put a note out here to say - beware!  I know a number of people who have lost data after trying to compress VHDs with the "Compressed Folders" feature of Windows XP.  Per KB301325:

When you create a compressed folder (ZIP file) that is larger than 4 gigabytes (GBs), the file may no longer be readable, and may become corrupted. You do not receive any error message when you create the file, but you cannot read the file after you create it.

Ouch!  This is why I always use WinZip (support for larger than 4GB files was only added in WinZip 10.0 and later).


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  • I use 7-zip (, which has the additional benefits of having a CLI in addition to the GUI, being freeware, and of course for .7z support, which can get you better compression ratios on most files than .zip (which was originally designed for text files).

  • Agreed. 7-zip is the best. I've been using it for years. Only bad thing about it is that there hasn't been an "official" release for a very long time. It's always in beta status. Not sure how relevant this is anymore since everything is in beta anyway....but it does make me hesitate when I'd like to install the latest version on a work machine.

    Down with Winzip! Winzip is the Adobe\Norton of the compression world! (Ok not that bad)

    Also don't forget Universal Extractor:

  • Oh, forgot. The above comment about 7-zip being freeware is not true. 7-Zip is OpenSource. There's a vast difference between freeware and OpenSource. Calling 7-Zip "freeware" is an insult.

  • Allegedly WinZip now supports LZMA and will also open 7z files.

  • Thank you for this blog posting.  It is informative and some readers wouldn't have guessed that 6-year-old KB article without it.

    Meanwhile though, don't you have opinions about these:

    > You do not receive any error message when you

    > create the file, but you cannot read the file

    > after you create it.

    Even if the only people who read error messages are antisocial geeks, is it really sociable to cause corruption in silence instead?  Who benefits?

    > Last Review : October 18, 2001

    Sure, it doesn't need a review because it hasn't changed in 6 years.  But *why* hasn't it changed in 6 years?  The only people who were hurt by it were pirates downloading movies, so Windows should do the same thing to them that viruses would do to them?

    For some magical unknown reason I think I haven't been hit by this particular kind of corruption.  Just on principle, I can't help wondering at the sense of priorities that make this data loss a "won't fix".

  • I find 7zip non standard and slow.  It might have good ratios, but none that make it more attractive than WinRar.

    While 7Zip is a significantly more open standard than WinRar, I don't find that adequate compentation for making an archive that practically no-one else on the planet can open (let alone identify).

    I'll stick with multipart WinRar when I need to compress data that large.  I'd probably also create a 10% par2 set too, just in case of a media failure.  You still reduce the file while providing some extra insurance.

  • Do you know if Vista's compressed folders are ok?

  • Lorenzo: in the Vista Beta/RC phase, Compressed Folders was horrendously slow. I've no idea if it was fixed for RTM, but WinZip was orders of magnitude faster.

    I'm fairly sure WinZip 9.0 SR-1 could also handle 64-bit ZIP files and large (>4GB) files within a ZIP. The ZIP64 scheme goes back to PKzip 4.5 according to the 'version needed to extract' field documentation in the ZIP spec at

    Norman: you know how MS change control works. A problem in a released product is fixed only if a customer asks for a fix. The workaround for this problem is of course 'use a different ZIP product', of which there are plenty, so probably no-one has asked for a fix and even if they had the servicing team would not have agreed to do one. Service Packs almost always only include a rollup of hotfixes, with a few other targeted fixes - XP SP2 was exceptional, but concentrated on security, WiFi and a few other areas. A fix to this was never going to get into the service pack.

  • DosFreak: Well SORRY! :P  Open Source is, technically, a subset of freeware.  I consider any free software I don't have to pay for "freeware".  It also helps I didn't know it was OSS.

    Moz: Yeah, but I just don't like WinZip.  Probably because my cousins' have it on their comps and it makes you wait 30 seconds every time you run it before you can do anything until you buy it.

    Norman: The corruption happens when you CREATE ZIPs using Compressed Folders.  I imagine there's no problem extracting large ZIPs made with other applications.

    Xepol:  7Zip is only really slow if you choose the highest compression ratio, but even then I find the slow speed acceptable, since you only usually need to compress once, and the decompression speed is what really matters (and I find it acceptable).

  • Agreed with Dan, all Open Source software IS freeware but not all freeware is open source obviously.

    There are lots of good closed source freeware apps our there including Opera, Trillian Basic, Irfanview, Spybot  Search & Destroy and CDBurnerXP Pro.  In the past I would have included µTorrent and all the sysinternals tools  but those are now owned by non-trustworthy companies which is of course the major downside to closed-source freeware.

    Also let me chime in my own recommendation for 7-Zip.

  • Dan -> If you don't use the highest compression ration out of 7z, then you might as well use something more common.  My experiences with 7z to date have marked it slow not just in compressing but in decompressing as well.

    Frankly, I can't see why I would want to use it tho.  Back when Arj and Zip and Zoo were all new, 10% space reduction was a huge deal with floppies being the storage media of choice and 1200baud being the high end speed of the day.  Now, do you really think shaving 100k of a 600mb file really justifies the huge archiving delay or the fact that almost no one has any clue what a 7z file is??

    I guess I just don't see what problem 7z is the solution to.

  • It can be the difference between fitting all of your files on 1 CD vs 2 CD's...

    Any person that doesn't care about decent compression will just use zip. For those of us that need better compression we use that tools that do so. .7z\.rar are hardly the best compression formats but they do have the best GUI programs and options than other formats that have far better compression.

    Besides, you don't have to use the highest compression options for .7z. Usually doing so is a waste of time. The default options are just fine and compress better than zip.

    As far as no one knowing what a .7z is. Judging by my users at work they don't even know what a .zip is. All they care is if the click on it and can open it that it does so. As long as the OS supports it then it's fine. Sadly most people use Windows which by default AFAIK only supports .zip.

  • This "compressed folders" feature is not the same as the ntfs compression, right? I remember I used to compress lots of folders and files using the ntfs compression without any problem...

  • Friday, May 25, 2007 7:33 AM by Mike Dimmick

    > in the Vista Beta/RC phase, Compressed Folders

    > was horrendously slow.

    In RTM, it seems to be horrendously slow in unpacking, but it's also horrendously slow in copying an ordinary folder.

    Furthermore, if the zip file was copied from another machine, the "help and support" instructions say that the user should enable Outlook Express and then use Outlook Express to unblock the zip file, which is a pretty nice garbage combination of garbages.

    [In XP]

    > The workaround for this problem is of course

    > 'use a different ZIP product'

    Oh yeah, and that's true in Vista too.

    Now is there a way to disable the broken built-in functionality so that XP will *only* use a different zip product...

  • Hey,

    Just wanted to say thanks for all the tips you've posted. You've saved me tons of time and I really appreciated. Thanks for the great work!


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