What's the standard format for sending an email?

I bought a new computer recently with Windows Vista. I'm using Windows Mail (having previously used Outlook & Outlook Express). Everytime I create an email and send it, I am asked if I want to send the email as unicode or send as it is. I always just send as is. I was wondering however what settings I should have my email at to prevent this message constantly coming up. I have defaulted my email to send in HTML, using Western European ISO.

Try Unicode UTF-8 instead of Western European ISO. Try sending a few test messages to people who you can ask to report back to you in case of any problems.

Thanks Clubman, but I'm still getting the same message - Message Character Set Conflict.

Sorry - I was assuming Outlook Express but see now that it's Windows Mail. Never used that so can't advice. Have you Googled for info about this issue?

Googled it but still didn't come up with the solution. Thanks anyway.