stsadm -o enumtemplates > templatelist.txt & for /F "tokens=1" %i in (templatelist.txt) do stsadm -o deletetemplate -title %i & del templatelist.txt

Found this from a cool blog entry by Rob Nowik
http://rnowik.com/blogarchive/1149116400/

 Cool and it work on MOSS 2007 :)

 Thanks Nowik.