Windows 7 blocks utorrent

[Anewr]

Hi. So I have been running utorrent periodically on my windows 7 for the last couple of months. However, starting today I can not run utorrent. A message pops up saying that it is blocking the use of it and when I use try downloading it again (i unistalled it to see if re-installing it would work) but when I try opening the downloaded file windows blocks it as a potential harmful file however when I downloaded it before, this message never popped up. How do I fix this? Thanks!