What for do you want to change:
Don't you have any problem to change httpd.conf only?
I think install/start.html and htdocs/xampp/*.php must be changed too.
?
For making any directory work as webfolder, just these two settings have to be made, because this is the the apaches main setting for webroot.
What for do you want to edit start.html? You can replace it with your own, but in fact everyone should know that.
Now you can tell us whats wrong with a better description, if theres still any problem with your XAMPP.
@schamock:
Did you restart apache, and/or did you really edit the httpd.conf (and not httpd.old.conf for example)
Nope means no.
greets, Flo