I download and install new version of windows

Hello,
i download a new version of windows live messenger and then install it and it take too much time
and when downloading and after that installation comletes then the installation rolling back:( i dont know why.i was waitning that now i will be able to chat with ma frends but.........and then i installed it again and when 100% installation got complete i cancel installation before rolling back of installation.i also open messenger once.but on the next day when i click on messenger icon then it gives an error.i dont know wot is the problem plzzz help me orr guide me about this problem
thank you