SharePoint 2010 Upgrade issues

Upgrading to SharePoint Foundation 2010 on TechNet
http://technet.microsoft.com/en-us/library/cc303309.aspx.

Visual diagrams of the upgrade process can also be found on TechNet
http://technet.microsoft.com/en-us/library/cc288775.aspx

Joel Oleson's helpful insights
http://www.sharepointjoel.com/Lists/Posts/Post.aspx?ID=296