XP Zip Problem

[brucefulton]

I have created a large zip file on Vista using the send to compressed
folder option. It consists of a virtual machine and supporting files,
so it's 2.5gb uncompressed and about 1gb compressed. It will unzip on
Vista and also on a Mac OS-X using unzip. It will unzip on XP using
Winzip and PKWare Reader. However, the native XP unzipper accessed
from file explorer fails, reporting an unknown compression method. If
I zip it using XP, then it is noticably larger than the Vista-created
zip file.

 

[Twayne]

I have created a large zip file on Vista using the send to compressed

folder option. It consists of a virtual machine and supporting files,
so it's 2.5gb uncompressed and about 1gb compressed. It will unzip on
Vista and also on a Mac OS-X using unzip. It will unzip on XP using
Winzip and PKWare Reader. However, the native XP unzipper accessed
from file explorer fails, reporting an unknown compression method. If
I zip it using XP, then it is noticably larger than the Vista-created
zip file.

Most likely what you have is a mix of supported zip types in the
machine's capabilities. XP's native zip is also a "loose" zip format in
an attempt to work with as many zip file utilities as possible.
However, if the zip was created by something newer than XP's zip
abilities (as in Vista's capablities) then it's entirely understandable
that XP cannot unzip it because it doesn't know about the algorithms
that were used to zip it. I don't have any experience with PKWare's
REader, but Winzip would likely be able to unzip it, as you indicated.
In fact, under the right settings, the lastest Winzip as I understand it
can create zip files that even Vista cannot read, but I don't know that
for a fact. Winzip even has a proprietary zip algo in their latest
versions.
Whenever you have the choice, always choose "Legacy" for the zip type
if the files are going to be moved around. That pretty much insures
that no matter what tries to unzip it will succeed. It won't create the
smallest possible zips, but it will create zips that most any zip
program can work with and unzip.

In other words, it sound like all is normalI just used a lot of words to
say that. <g>;

HTH,

Twayne

 

[brucefulton]

Most likely what you have is a mix of supported zip types in the
machine's capabilities.  XP's native zip is also a "loose" zip format in
an attempt to work with as many zip file utilities as possible.
However, if the zip was created by something newer than XP's zip
abilities (as in Vista's capablities) then it's entirely understandable
that XP cannot unzip it because it doesn't know about the algorithms
that were used to zip it.  I don't have any experience with PKWare's
REader, but Winzip would likely be able to unzip it, as you indicated.
In fact, under the right settings, the lastest Winzip as I understand it
can create zip files that even Vista cannot read, but I don't know that
for a fact.  Winzip even has a proprietary zip algo in their latest
versions.
   Whenever you have the choice, always choose "Legacy" for the zip type
if the files are going to be moved around.  That pretty much insures
that no matter what tries to unzip it will succeed.  It won't create the
smallest possible zips, but it will create zips that most any zip
program can work with and unzip.

In other words, it sound like all is normalI just used a lot of words to
say that. <g>;

HTH,

Twayne

If I'd used winzip to create it, I could see your point, but Vista is
creating a zip that XP can't read and there is no "legacy" compression
option. Since we're now up to xp SP 3 and backwards compatibility
vertically to MS own utilities is traditionally supported, I would
think there would be a patch to one or the other that would ensure
interoperability, as MS has done with any number of support utiliites
that need to interoperate in mixed-mode environments.

I'm hoping an MVP will either confirm that there is a known
incompatibility so I can move on, or point me to an appropriate hotfix
to take care of this.

 

[News Reader]

Go get 7-zip, a free program and it can open all manor of zip files.
www.7-zip.org

 

[brucefulton]

You also are missing the point. I am trying to create, using microsoft-
supported utilities, a zip file I can post that users of XP can
download and unzip without having to download third partysoftware.

I have no problems unzipping the file. People who download a 1+ gb
file from the internet who then can't unzip it using XP are the
problem. There is no opportunity to tell them in advance that they
have to download a third party program to read the file. Unless you
have a means to send everyone on the planet an email telling them to
download 7-zip, we still have a problem.

Let me repeat -- I am not looking for a workaround. I can unzip the
file. I am the producer of the file, and XP users can't unzip it. I am
looking for an authoritative answer to the question of whether this is
a known bug in XP, and then whether there is a hotfix that can be
downloaded, either for Vista on the zipping end, or xp on the
unzipping end, that will take care of it.

I don't need to be told to download a file that I already know will
unzip the file. That is not the problem.

If this is a known problem, then I need an authoritative response that
references a hotfix or Microsoft KB article that addresses it.

If this is a previously unreported or unresolved bug in XP, then I
need an authoritative answer to that so I can plan distribution
strategies.

 

[Kelly]

Error message when you extract a compressed file that has a .zip file name
extension on a Windows Vista-based computer: "This file was compressed using
an unknown compression method" http://support.microsoft.com/kb/938319


--

All the Best,
Kelly (MS-MVP/DTS&XP)

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