gtalk windows application does not support non-gmail account

You can sign up Google service using your non-gmail email account, but you can only use gtalk widget if you are using non-gmail account.

 

I also found one interesting thing that if I mouse over my friend, who is logging thru widget with her non-gmail account, in my Google Talk window, I see she is actually using 3ux4794qhrxxx@id.talk.google.com

So looks like when you are using widget with non-gmail account, actually google assign you a special/temporary gtalk account.