
I worked hard(not really) to make things simple again. Yahoo corporate removed the original small installation utility from their website forcing all users to install their bloatware yahoo messenger/toolbar; and so after YEARS of a lack of an easy online solution, I reconstructed a stepless installation from available online methods. Simply run the exe to restore Yahoomail as the default mail application in Internet Explorer including shortcut capabilities :-)
mirrors:
http://www.filedropper.com/yahoomaildefaultemailapplication
http://rapidshare.com/files/130756520/YahooMail_Default_Email_Applicatio...
http://files.filefront.com/YahooMail+Default+Email+Anexe/;11122007;/file...
enjoy!
p.s. further information inside exe (compressed rar) - tested on Windows XP.