can't open .zip, only starts .cpgz cycle

Firstly, sorry if I'm posting this in the wrong spot, I'm new. But I also heard this problem may be due to leopard.

I was emailed a .zip file that I really want to open but when I try to unzip it only creates a .cpgz file then then ..cpgz or another ..2.zip
I've tried double clicking the .zip and opening normaly and stuffit and opening it in windows xp
BTW it's a file I'll need to open in my xp partition if that makes a difference, (unfortunately I sometimes need to use xp as some apps such as autocad don't run mac) i just don't connect xp to the internet.