Help with email notification.

Hi,
I started using DynAdvance email notifier for notification of my Yahoo mail and apart from lack of sound it was working fine. It then stopped notifying and when I opened the programme and selected read mail instead of signing me in it took me to the Wrong user name or wrong password page. I resubmitted my details but to no avail so I reinstalled the programme, again to no avail.
I then tried half a dozen different email notifiers but each one malfunctioned in one way or another. I am wondering if I have inadvertently corrupted the registry when doing a scan for registry issues. I have done a system restore as far back as I can but no change.
Has anybody any ideas what I can do to solve this problem?
I am using Windows XP and IE8.
Regards Alex