[The Fifth Horseman]

A switch (which may be called a flag, an option or an argument) is nothing more than an extra element you type in after the rest of the command
What I meant is that you're either entering

mount d: c:/kyracd/cd
mount c: c:/kyracd/

or

mount c: c:/kyracd/

when what you're supposed to enter is

mount d: c:/kyracd/cd -t cdrom
mount c: c:/kyracd/

(obviously C:/kyracd may be whatever other directory you unpacked the game to)