Whats the difference in Windows live messenger id and my yahoo id?

i sing into my hotmail account under a user name and password so i can use windows live but when i try to use my yahoo id it wound let me sing in, ant help please I'm new to messenger

Whats the difference in Windows live messenger id and my yahoo id?ie 7

messenger is microsoft, yahoo is not, its like trying to log into ebay with a yahoo account.

hotmail is also microsoft incase you diodn't know