Solve : Default mail constantly opeining?

When I first got this computer and turned it on outlook express popped up, I closed it and then it popped up again, and it kept POPPING up constantly.  Then it stops and an hour goes by and it doesn't pop up. Then all of a sudden it goes off again. I tried to figure it out:  options, tools, internet options unchecked any boxes that i thought might be causing the problem, Google it to and still nothing. so I just decided to live with it. Okay so now i get At&t DSL and Yahoo becomes my default mail so now I'm getting constant browser windows popping up with yahoo mail i mean I'm getting like 20 windows popping up, sometimes they pop up slow and can close them down, then sometimes it's so fast i got 27 windows up at one time. Sometimes and hour goes by and nothing. *censored* is this. I have scanned, scanned and rescanned with all kinds of spy ware detectors and anti viruses, REGISTRY fix and have had problems and fixed them but it has not fixed this. Why is this happening.  Can anyone help??? I don't think this is a virus and I can't be the only one who has had this problem!!! If you can DOWNLOAD and install Malwarebytes for free as well as get AVG Free Antivirus if the malware or virus's dont block you from doing this. Many virus's will protect themselves from DELETION by blocking programs that can delete them.

http://www.malwarebytes.org/mbam.php

http://free.avg.com/download-avg-anti-virus-free-editionBoot your pc into safe mode and run a antivrus and malware scan
then once the scans are complete and you have gotten rid of what it has found
simply reboot normally and you should be fine.