I suddenly find when I click on Send/receive the message says downloading emails and downloads say one or two but the number being downloaded keeps rolling.

At one time it said 7,000 emails plus.
I then realised in my inbox it was downloading duplicates of old emails - hundreds of them as long as I had the email receive thing open.

How can I stop this please. I am on TalkTalk and have Windows 8.

I think I have my settings to receiving emails ever ten minutes so presumably this downloading of hundreds will happen automatically every ten mins?

I've tried logging off and on again - no difference.

Someone said go to Tools and email account but when I hit Tools I cant see email accounts listed.

You need to get in contact with your Email Service Provider (TalkTalk?) and make sure you have configured the email application correctly according to them.

For example:
How do I set up Windows 8 Mail for TalkTalk email?
and
http://help2.talktalk.co.uk/set-and-manage-your-email/how-do-i-set-windows-8-mail-talktalk-email What are TalkTalk's email settings?
http://help2.talktalk.co.uk/set-manage-email/what-are-talktalks-email-settings

You would look at those settings and whatever you have setup and make sure they match.