Rundll32 error

Before defragging, i shut down all applications using CTRL + ALT + DEL. in the last couple of days, i have had Rundll32 in the list of apps twice, and when i try to close it, it says its not responding, and i cannot get rid of it.
And defrag will then restart every 3 minutes or so.
there are also some things in this list i have no idea what they are, one for example, is named ‘ShowBehind’. anyone know what this is?
is there a way to delete things from the selective startup list via the registry somehow?
I am running W98.
Thankyou.