This is a problem I noticed some time ago on my various machines I use, and just never took the time to understand why it was happening. Today, I was unzipping a relatively small zip file (~2mb) but it had quite a few files in it, and it amazed me that WinZip was taking 1-2 seconds PER FILE to unzip them.

After some investigation, I found the following FAQ page on WinZip's site: http://www.winzip.com/xattmgr.htm

It turns out that starting with Windows XP SP2, an Attachment Manager service was added that provides some security for downloading of potentially malicious file types from the different zones.

so I started thinking a bit more about it, and I can understand the Attachment Manager "watching my back" if I were unzipping the file directly from the downloaded location.  But I was having the same issue with files I had saved to my Desktop or elsewhere.  Well, if you read the knowledge base article linked at the bottom of the WinZip FAQ page above, you'll see that XP and Vista remember the zone the file was downloaded from, and treat it as if it still existed in that zone when allowing access to it.

The fix mentioned in the knowledge base article is to add/edit the registry key at: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Attachments

Edit the value for the "SaveZoneInformation" and set it to 2 to disable the remembering of the file's original zone information.

I implemented this change (I had to create the "Attachments" Key, and the "SaveZoneInformation" value), and re-ran the previous un-zip on my small zip file, and it finished in under 5 seconds...