Have you tried looking in the control panel? I don't know if Vista still has that, I only used it once when setting up my sisters new laptop, it seems really confusing to me.
I never used vista. using my XP SP2 experience I can suggest the following -
right click on My Computer > select Properties>select Hardware tab>select Device manager>double click on bluetooth device> enable it
but you may not have this options in Vista. I told you I'm not sure about Vista.