False Positive?

I was signing into hotmail and I got this message

Maybe your system has an infection?

Download Malwarebytes’ Anti-Malware (MBAM) then get the latest definition updates then run a Quick scan and have it remove what it finds:
http://www.malwarebytes.org/mbam.php

Post its log here if you like.

Go to Secunia Online Software Inspector then run it to see what applications are vulnerable:
http://secunia.com/vulnerability_scanning/online