how to force a sharepoint 2010 site to use 2007 UI

We have sites that were created in Sharepoint 2007 and when we upgraded to Sharepoint 2010 our users wanted to keep the 2007 UI look and feel.  So these sites still look like they did in 2007.  Now we need to create a new site for this customer and they want this site to also look like the 2007 UI.  So my question is: is it possible to create a new site in Sharepoint 2010 but somehow force it to have the 2007 UI?

thanks