Not sure what exactly you are looking for. Unconfiguring in the sense you need to uninstall BizTalk server 2004. If that is the case then open admin console and delete/stop all the applications and start uninstalling the bizTalk from add/remove program.
Otherwise open windows services and stop all bizTalk related services and start uninstall.
If you are facing an issues please let us know.
Asheej T K