Neil,

A possibility is that your PC installation may need tweaking. Below is an extract from MS on the subject.

Since IE 4, there has been a desktop shell helper object called Shell.Application.

This object lets you manipulate the desktop and access other system things
(couldn't think of a better description).

Examples of things you can do:
Create explorer windows 
Tile, minimise and restore the desktop 
Copy/Move files displaying the standard progress animation 
Execute commands associated with applications.
 
Set ShellApplication = CreateObject("Shell.Application")
 
Win 98, ME and W2K users should have no trouble with this object.
If you have Win95 or NT4 and installed IE 5 without upgrading from IE 4
then you may get an error when trying to use this object. If you have
already installed IE 5 then try this command:
For NT
IE5Setup.exe /C:"ie5wzd /e:IE4Shell_NTx86 /I:Y" 
For 95
IE5Setup.exe /C:"ie5wzd /e:IE4Shell_WIN /I:Y"

For the full article go to
http://groups.msn.com/windowsscript/shellapplication.msnw, but there isn't much more than the above.

Using the file system object or WScript.Shell do not work as they don't understand Zip files as folders. If you can get your installation sorted the Shell.Application method works well.

HTH

Alan