Vista - Windows live messenger installation problems

greetings everyone,

i tried installing windows live messenger onto my laptop, i canceled the instalation and tried to install again, it now says that i have the programme, when i can't locate it at all, on my computer. i've used CCcleaner, but that hasn't worked. any advice? i've also let my friend connect to our wireless internet, he downloaded windows messenger as well, do you think that it says it's on my computer because he downloaded and installed the same programme on his computer using MY internet? please help, thankyou.