Change your setting to administrator and it will work- there are a few threads around if you want to look them up (type 'castle link vista' into the search box).
I am running castlelink on both vista 32 and 64..Just run the installation program as administrator as they suggested (or noted on a thread somewhere here), for vista 32 this is all you need. but for 64 you need to right click the properties of your shortcut (to launch castlelink) and under "compatibility tab" run it as compatible with Windows XP SP2....it should recognize the ESC