Downloaded Theme

i have just downloaded a new theme,and it
added a picture,when my computer boots up
and when it shuts down.The picture at shut-
down has replaced my message telling me "it
is safe to shut windows down"i no longer
want the theme on my computer,i can deleted
the theme,but can not get rid of the opening
picture or the closing picture

in win98 it is logos.sys and logow.sys for shutdown(open them with paint and you will see). Can't remember what it is for startup.

just set the desktop theme to default