Thank you soooo much! That explains it. Everyone said it was because I use Mac!

So I have to go through a training course to solve this one problem? How do I find the topic I need?!

I'm new to Sketchup. I work on a Mac (only two months old) and I cannot open attachments sent to me from windows machines. What am I doing wrong? I'm working on a group architecture project at school and I can't review the other groups sketch ups unless they put it on a flash drive. The attachments have ".skb" i.d.s thanks if you can help!