Convert a Sub-site to a Site Collection

REM Create a test web for exporting
stsadm -o createweb -url "http://intranet/testweb" -sitetemplate "SPSTOPIC#0"

REM Export the test web to the filesystem
stsadm -o export -url "http://intranet/testweb" -filename "c:\testweb" -includeusersecurity -versions 4 -nofilecompression -quiet

REM Create a managed path for the new top level site
stsadm -o addpath -url "http://intranet/testsite" -type explicitinclusion

REM Create an empty site with a default site template (note that if you don't specify a template you have to manually activate the required features)
stsadm -o createsite -url "http://intranet/testsite" -owneremail "someone@example.com" -ownerlogin "domain\username" -sitetemplate "SPSTOPIC#0"

REM Import the site
stsadm -o import -url "http://intranet/testsite" -filename "c:\testweb" -includeusersecurity -nofilecompression -quiet