SQL2005 doesn't have Extended Events, so you'd need to use the trace flag option, which won't get you your information from 15 days ago. There's not much you can do there, at this point...
For SQL2008, yes, once you've run the first query, copy the *entire* XML output and paste it into the 'Put your deadlock graph here' area. You may also need to go through and double up any single quotes in the XML.
Further reading on troubleshooting and finding deadlocks:
http://blogs.msdn.com/b/bartd/archive/tags/sql+deadlocks/default.aspx
Jason