>I have been using Pkzip 2.5 for my DOS application for taking backup of data.
>
>Recently, we are getting the following error in both Windows XP & in Win 7
>
>PKZIP: (E15) Can't open XXXXX.ZIP for write access!
>
>The named .ZIP file is read-only or locked by another application and can
>not be modified. This may also occur on a Network drive if you do not
>have adequate access to that file to allow you to modify it.
>
>
>
>I have used Unlocker.exe & attrib -s-h-r.
>
>The zip file is created using other methods in the format ?????.zip
>
>Any help would be appriciated.
>
>Rakesh

Does someone have the ZIP file open in Windows Explorer? (it shows up in Explorer as "compressed folder" into which you are able to navigate as a normal folder)
Have you checked on possibility of an antivirus blocking you? (e.g. you are updating ZIP file on network location, the moment you release access [i.e. close the file], host computer initiates an automatic scan -- blocking further updates until it finishes)
If the file isn't local to the computer (i.e. it resides on network share), you're more likely to run into conflicts.
Make sure you've got full access to the containing folder -- sometimes you get this effect if you've don't have sufficient rights to the folder in which the ZIP file is contained.
If the file is on a network location, check both the security and sharing permissions of the file as well as containing folder.