Virtual Hard Disk image for MOSS from Microsoft http://www.microsoft.com/downloads/details.aspx?FamilyID=67f93dcb-ada8-4db5-a47b-df17e14b2c74&DisplayLang=en
So you want to install WSS on Vista - here are the steps from those lovely people at Bamboo solutions
http://community.bamboosolutions.com/blogs/bambooteamblog/archive/2008/05/21/how-to-install-windows-sharepoint-services-3-0-sp1-on-vista-x64-x86.aspx
