Windows 7 Client Mail Default

I'm trying to open a site, but I keep getting a message that says " client mail default not set up properly " What do I do?

 

Thanks. I've been using IE Yahoo for many years and I never had this problem until a month ago. Now this is the second time. I'm not sure what the consequences would be if I switched to Thunderbird. Could I still use Yahoo? The only email address I've ever had has been Yahoo and that's been 20 yrs ago. It would be impossible to change it now.

 

This thread will show you how to check the settings for the default mail client.

http://answers.yahoo.com/question/index?qid=20091207132341AA3ja1m

This is worth a try but I suspect that unusual activity like this is due to Malware or a Virus.
So, if the above doesn't work please go to our Malware and Virus forum, read through the introduction and start a new thread with the requested logs.