When I try to open a document library or list with Windows Explorer, I often encounter the following error:

> 
> Your client does not support opening this list with Windows Explorer
> 
> 
> 

The error happens to me on some machines, but not on others. I've experience this problem on several different set-ups, with different browsers (IE6, IE8 and IE9) and different operating systems (Windows Server 2008, Windows 7). However many of my colleagues, my clients and even sometimes I have been able to successfully use this feature on other machines.

So my question is:

**What settings do I need to enable in Windows / IE to ensure that Open with Windows Explorer is available?**

and related, **Can I get Open with Windows Explorer to work with IE9 64-bit**

(Some notes; I'm on SharePoint 2007 with Single Sign On, not integrated authentication)