here is a quick and easy way to pin a gmail application shortcut into your win7 taskbar using googe chrome.

1. create a new shortcut by right clicking inside a folder (like desktop or documents) followed by choosing: new > shortcut
2. use the following string on the location field: “%appdata%\Local\Google\Chrome\Application\chrome.exe --app=https://mail.google.com/mail”
3. after the shortcut was created, change the icon for shortcut by right clicking on it and choosing properties > change icon (i have downloaded the gmail icon from http://iconexpo.com/2009/02/free-gmail-icon-new-version)
4. drag the shortcut to the taskbar in order to pin it
5. click on it, it will first open a new task on task bar but after gmail loads it will merge to the one you have already pinned (which is separated for the normal chrome task on the taskbar)