I'm pretty sure reinstalling will just cause the same update to be applied. Do what I said before, but look for an update for Windows Defender. De-select the update. Runs windows updates and see what happens. If it solves the problem there are some options for you. If you have a good antivirus or antimalware program already, you could turn off Windows Defender. If you don't currently have an AV program, download and install MSE. It turns off Defender automatically and does a really good job for a free program. If the problem remains, definitely leave Defender on. It provides some extra protection from spyware.
EDIT: Be advised that some will always disagree with ever turning off defender unless MSE is installed. The choice is up to you. Just wanted to let you know that some will disagree with me and its hard to say who would be right in this situation.