Welcome to Justanswer.com, my name is Dustin.I'm sorry to hear about the issue you are having, I will do my best to help you resolve it.
When you say you have a mac desktop, with windows 7. Thats a bit confusing.
Does your mac desktop have an apple symbol or logo on it?
Or, is your machine a dell, or toshiba, or HP, or Asus, or some other brand?
Excellent.. In that case, this link will be of interest to you.