For another, they don't use "English" phrasing constructs, because they're American.
Yep, accent/dialect is a dead giveaway. I have been tempted to use my best impression of Hank Azara as Apu from the Simpsons the next time "Windows" calls. So far I've only had 1 "Windows" call and didn't have the time to play with them when they called. What I've thought about doing is this:
[apu voice]: I am glad to be you are calling. I am Mahatma from the Windows India. I have been monitoring your computer and you have the virus. You need to be installing the teamviewer so I can be having the remote access to fix the problem. But you are to be giving me your credit card number so I can be scamming you.
That should do the trick, unless they're in Bangladesh or Pakistan.
If I had even more time and ability I'd set up a Windows VM for them, but I really don't know very much about setting up a VM and don't have a Windows VM lying around. Wonder if I could set up a live CD of XFCE or something as a VM for them.