You might be better off asking this question in the Windows XP forum. This is the Macintosh side of the house.
Having said that, try going back to the Incredimail program ( I do miss spelling that correctly) and see if you can recover any of your mail. I assume you have current Anti Virus software with Up to date Virus definitions. Take a look at the Yahoo account and see if there is anything left in that In Box. Stuff for a new program/new account does not normally get moved from one place to another, it normally gets copied. Chances are you may find your stuff back there on Yahoo.
Hope you do, good luck
I downloaded from an American friends e-mail the programme 'Incredimail'. My inbox was automatically transferred to it on membership. I sent a couple of e-mails then a warning came up to say a worm had been detected. I cancelled the Incredimail programme and therefore lost all of my 'inbox' with photos of kids & friends & everything! Checked my recycle bin & it's not there. Anybody any clues? My e-mail is BT Yahoo and runs with Windows XP on a Dell Dimension 2400 and I'm a novice as you've probably guessed!