Please help I can't download emails on my mac

Hello,
Please will you help me with this predicament: I cannot access any downloads from my gmail emails. They go to download and then quicktime says it is unable to open them. it comes up with the following message:
'The document "HowaRealManTakesoffhisUnderwear-1.wmv" could not be opened. The movie is not in a format that QuickTime Player understands.'
Is there anything I can do? They open straight away when opened using microsoft computer. I have a macbook pro!

Thank you very much in advance for any help you can give me.