check out this freeware :
http://www.snapfiles.com/get/poppeeper.html
it will sit in your taskbar , watch all your e-mail accounts and notify you when you receive a mail in any of your accounts. It can watch POP, hotmail, yahoo and many other types of accounts.
It also lets you see previews of the mail so that you can delete huge spam mails on the server without having to download them, read your mail, and has a lot of other features.
It is very customizable, the GUI is very well thought and it is spyware free.
If you want it to watch your gmail account, just enable POP access in your gmail settings.
