Are you getting this error trying to install the WebDAV extensions on your Windows Server 2008 box?
The IIS 7.0 CoreWebEngine and W3SVC features must be installed to use this product.
It could mean that you tried to install the wrong architecture (x86 vs. x64). Noob.
(Of course, I haven’t just spent the last 5 minutes working that out.)
Tatham Oddie 