How do I create virtual forums in 5.0? The switch as it used to appear in earlier versions is no longer there.

In 5.0 the setting for Virtual Forums is made at the individual Folder level. EDIT the folder(s) in question, select "Basic folder appearance & hidden files" from the "Other Folder Settings" drop down list.

then check:

Make this folder a virtual area (Backpath links inside this folder go no higher than this folder.)

While there is no longer a sitewide setting, the advantage is that now you can make any folder at any level a virtual forum. Virtual Forums are no longer restricted to the Top Level of the site.