How to retrieve my Gmail password, from Google chat?

Try my other suggested method first, because once you reset your password, you won't get back the old one.

If you can get to the gmail web interface, and it sounds like you can, then you should be able to add a recovery email address to your account.

Go to the gmail web interface, click the account drop-down (it'll be your name or username, near the top right), and choose "account settings."

This will take you to the Google Accounts page. Under the "email addresses and usernames" section, you should be able to click "edit" and add a new email address to your account. Use a non-gmail address. It sounds like you lost some other accounts too, so you may need to create a new yahoo, hotmail, or other such account. Don't use anything like mailinator since somebody else could get access to your account.

Once you add the secondary email address, you'll need to confirm it by checking that email address. Confirm the address. Now, go open a new browser session (different browser, incognito mode, other computer - whatever). Go to gmail.com, and click on "can't access your account." This will take you to a form where you should be able to send a reset link to your alternate email (which you just added).

Once you receive the reset email, you'll be able to choose a new password, and should have full access to your email again!

Alternate answer: I'm posting this separately because it's an entirely separate method. If you're using the standard Gtalk client, with the password remembered, there is a tool which can actually tell you what the password is.

Install System Info for Windows (SIW). It's free for non-commercial use, and has a lot of handy utilities.

In the Gtalk client, choose to log out. (Click the down-arrow next to the status message box, then choose "log out.")

Now, open up SIW. Click the "Eureka" button on the toolbar - it looks like a sheet with a magnifying glass over it.

This will open up a dialog which lets you reveal the password in almost any standard password field obscured with dots. Make sure the Gtalk window is showing with you signed out. In the Eureka window, drag the magnifying glass icon over the password dialog, then let go. It should reveal the password in the Eureka dialog box.

As you can see, in this case the password was ExamplePassword. Hopefully if you do the same, you'll be able to recover your password. If it's the same as your password on the other lost accounts this may help you recover those as well!

Maybe give Password Spy a shot

Worth a go :)