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"

When you use WinZip to extract a compressed file that has a .zip file name extension on a Windows Vista-based computer, you receive an error message that resembles the following:

This problem occurs if the following conditions are true:

• You try to extract a compressed file that was created by using WinZip 10.
• The computer on which you try to extract the file has an earlier version of WinZip installed.

WinZip 10 uses a compression method that is incompatible with some versions of Windows and with earlier versions of WinZip.

To work around this problem, select the Maximum (portable) compression method in WinZip 10. To do this, follow these steps in WinZip 10:

1. Click File, and then click New Archive.
2. In the File name box, type the name that you want to use for the compressed file, and then press OK.
3. In the Add dialog box, select the files you want to add to the archive.
4. In the Compression box, select Maximum (portable), and then click Add.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

For more information about this error message, visit the following WinZip Web site: Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.