it's been a while since I last veiwed it, but if I remember rightly
you don't use the RMB but instead you have to pick a hot key
or hot key combination then make your selection from the menu using...

Have you had a look at the FREE video tutorial from this very site?

home>video training>free tutorials>basics-marking menus.

if it were modeled from a sphere, say, then it would be called

"subdivSphere1ShapeHistPoly", thats the one to delete.

go to window-> OUTLINER click the 'Display' menu and make sure 'shapes' is ticked, expand the grouping for that geometry name
and there will be something there relating to 'history'
select it and...